Methods for producing fertilizers and feed supplements from agricultural and industrial wastes

ABSTRACT

Integrated waste treatment and fertilizer and feed supplement production methods to be implemented at organic waste source sites, at remote treatment sites, or partially at the organic waste source site and at a remote location, whether in small or large scale operations. The methods are suitable for retrofitting existing organic waste sources and for treating the organic waste generated by a single source or by a plurality of sources. These methods provide: Reduction or elimination of emissions of acrid and greenhouse gases; effluents that meet discharge standards and that can be used in wetland and irrigation projects; organic based, granular, slow release NPK fertilizer of standard composition and size that can be supplemented with micronutrients and soil amendment materials and whose composition can be adjusted to meet demands and needs of specific markets; methane-rich biogas recovery for its subsequent use for heating, for power generation or for catalytic and synthetic processes, and feed supplement including feed supplement for cattle. The methods comprise steps for thoroughly separating suspended and dissolved materials, preventing gas emissions and capturing gases, and minimizing waste disposal. Fertilizer base is produced by mixing waste with at least one of a phosphate precipitating agent, a base, a flocculent, and optionally with an ammonia retaining agent and a densifier, subsequently separating and drying the precipitate.

RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/235,461, filed on Jan. 22, 1999, which claims priority toU.S. Provisional Patent Application Serial No. 60/072,372, filed on Jan.23, 1998, all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. The Field of the Invention

[0003] The present invention relates generally to the production ofcommercial fertilizers by treating agricultural and industrial wastes.More specifically, the present invention relates to a method forproducing organic-based, slow release fertilizers by processingorganic-based and industrial wastes.

[0004] 2. The Relevant Technology

[0005] Feedlots, animal barns, agroindustrial plants, municipal sewage,and farms that keep large numbers of animals are sources of enormousquantities of organic waste. The expression “organic waste source” willhereinafter refer to any of these sources of organic waste or to anysource that similarly produces organic waste, although perhaps indifferent quantities or by different activities.

[0006] The disposal of untreated organic waste causes serious pollutionproblems which include those due to the waste's high content ofchemically oxidizable components (expressed as COD, or chemical oxygendemand) and biochemically decomposable components (expressed as BOD, orbiochemical oxygen demand). When these pollutants reach bodies of water,either because they leach from disposal sites or as a consequence ofbeing directly released or transported into water bodies, theydeoxygenate the receiving waters and impair the receiving waters'capability to support aquatic life.

[0007] Acridity and high pathogen content add to the COD and BODproblems of untreated waste disposal. Acrid gases released into theatmosphere are not only unpleasant but they can also contribute to aciddeposition, global greenhouse effects, and ozone depletion.

[0008] According to background material provided by the US EnvironmentalProtection Agency (EPA), “animal waste, if not managed properly, can runoff farms and pollute nearby water bodies. Agricultural run off, rich innutrients like nitrogen and phosphorous has been linked to dangeroustoxic microorganisms such as Pfisteria piscicida. Pfisteria is widelybelieved to be responsible for major fish kills and disease events inseveral mid-Atlantic states and may pose a risk to human health.” DraftStrategy for Animal Feeding Operations, EPA Memorandum, Mar. 4, 1998.See also EPA To Better Protect Public Health and The Environment FromAnimal Feeding Operations, EPA release of Mar. 5, 1998. In particular,the relationship between swine production and waste management problemshas been reported in the Task Force Report No. 124, Council forAgricultural Science and Technology, Waste Management and Utilization inFood Production and Processing, October 1995, pp. 42-54, 110-121.

[0009] Notwithstanding the problems referred to above and otherdetrimental effects of the disposal of untreated organic waste, organicwaste has nutritional value for plants. Nevertheless, untreated organicwaste cannot be used directly as fertilizer because of theafore-mentioned problems. The alternative use of synthetic fertilizersis often adopted for increasing crop yield, but this solution carries atleast two undesirable implications. First, a strategy that relies onlyon the use of synthetic fertilizers neglects the problem of organicwaste disposal. Second, the manufacture of synthetic fertilizersfrequently requires consumption of considerable amounts of energy andpossibly expensive synthesis materials, sometimes involves pollutingsubprocesses, and may produce additional waste whose safe disposal isoften expensive. In addition, the fast release of most syntheticfertilizers causes leaching, which in turn leads to wasted fertilizerand the ensuing pollution problems when the leached fertilizeraccumulates in canals and other bodies of water.

[0010] The problems inherent to organic waste production and subsequenttreatment require economical processes which avoid the afore-mentionedenvironmental problems. The efficiency of these processes isconsiderably enhanced when, in addition to providing a practicaldisposal of organic waste, the processes convert the organic waste intoa useful product, such as commercial fertilizer, preferably aslow-release fertilizer. This conversion requires the recovery of thenitrogenous products in the waste and their conversion into a fertilizerthat can slowly release nitrogen in a form that plants can absorb.Because of the diversity of variables that determine the economic,chemical, and environmental aspects of this conversion problem, avariety of attempts to treat organic waste have been undertaken. Thepatents and other works referred to hereinbelow relate to methods thataddress aspects of the problem of converting organic waste into usefulfertilizer.

[0011] Methods for producing fertilizer have been disclosed inreferences that include the following patents and articles.

[0012] U.S. Pat. No. 5,593,099 describes a method for producingfertilizer from liquid manure or from sludge that includes mixing themanure or sludge with harvest leftovers and then grinding the mixture toa particle size such that the particles adsorb and absorb the liquidsubstance fully. An apparatus for producing the solid fertilizer is alsodisclosed.

[0013] U.S. Pat. No. 5,482,528 describes a pathogenic waste treatmentprocess to produce a useful product such as an amendment to agriculturalland. In the process, waste is combined with an acid and a base whichreact exothermically to thermally pasteurize the waste and add mineralvalue to the product. Materials such as fly ash agglomerate the product,and after grinding, the particles can aerate the soil. This patent is adivision of U.S. Pat. No. 5,422,015 that also discloses a pathogenicwaste treatment. The use of alkaline fly ash as an amendment for swinemanure has been studied by M. Vincini, F. Carini, and S. Silva, Use ofAlkaline Fly Ash as an Amendment for Swine Manure, BioresourceTechnology, Vol. 49 (1994), pp. 213-22.

[0014] U.S. Pat. No. 5,443,613 describes a method for producingsuspension fertilizer by first preparing an aqueous initial suspensionof the organic material and transforming it into colloidal form. Anammoniacal compound, such as anhydrous or aqueous ammonia, andsupplemental compound or compounds for providing the other desiredinorganic plant nutrients are added to and admixed with the acidifiedsuspension to produce a finished suspension fertilizer having thedesired analysis.

[0015] U.S. Pat. No. 5,411,568 describes a method for preparing granularslow release nitrogen fertilizer from nitrogenous organic wastes bycoreacting particulate dry conditioned nitrogenous organic waste andreactive ureaformaldehyde oligomer.

[0016] U.S. Pat. No. 5,393,317 describes a method and apparatus formaking organic based fertilizer, the method including mixing organicmaterial with phosphate, potash, or other inorganics and water ifnecessary. Acid and ammonia are also added to the mixture, andquantities of the various ingredients are adjusted to provide afertilizer that has a desired percentage of the major fertilizerelements for a specific crop.

[0017] U.S. Pat. No. 5,378,257 describes a process for organicfertilizer production that comprises mixing a batch of the waste matterwith nitric acid, crushing the waste water mixed with nitric acid tomake sludge, adding quicklime to the sludged waste matter, therebyneutralizing the waste water, and drying the neutralized waste matter.An apparatus for the production thereof is also disclosed.

[0018] U.S. Pat. No. 5,071,559 discloses a method for processing manureby adding an organic carrier liquid to the manure, concentrating themixture of manure and carrier liquid, condensing the formed vapor,anaerobically treating the condensate, and aerobically treating theeffluent from the anaerobic treatment.

[0019] U.S. Pat. Nos. 5,021,247, 5,021,077, and 4,997,469 disclosemethods for preparing high integrity natural nitrogenous granules foragriculture by processes that include the heating of natural nitrogenousmaterials under alkaline conditions until the materials develop adhesiveproperties.

[0020] U.S. Pat. No. 4,710,300 describes a method for processing oforganic materials containing nitrogen compounds, where the organicmaterial undergoes an anaerobic digestion with simultaneous liberationof biogas which contains methane and carbon dioxide. In this process,the liquid product obtained after anaerobic digestion is heated toboiling tenperature, ammonia is bonded as carbonate which is distilledoff, and the tail product from distillation is further processed to thevaluable product and clear water or is discharged as prepurifiedwastewater. Biogas production and anaerobic lagoon digesters have beendescribed by L. M. Safley, Jr., S. L. Crawford, and W. R. McLeod,Capturing Methane for Fuel and Other Strategiesfor Managing Swine LagoonWaste, pp. 38-41; L. M. Safley, Jr., S. L. Crawford, D. Nichols, and W.R. McLeod, Low Temperature Lagoon Digester for Biogas Production fromSwine Manure; L. M. Safley, Jr., and P. D. Lusk, Low TemperatureAnaerobic Digester, published by the Energy Division of the NorthCarolina Department of Economic and Community Development; J. R.Fischer, D. M. Sievers, and C. D. Fulhage, “Anaerobic Digestion in SwineWastes”, and E. J. Krocker, H. M. Lapp, D. D. Schulte, and A. B.Sparling, “Cold Weather Energy Recovery from Anaerobic Digestion ofSwine Manure”, in: Energy, Agriculture and Waste Management, edited byW. A. Jewell, (Ann Arbor Science, 1975) pp. 307-16, 337-52.

[0021] European Patent Application No. 79400246.9 discloses a method andfacility for deodorizing waste from pig farms and for transforming itinto manure. A mixture of the waste and a calcareous solution isdecanted and the separated liquid component is oxygenated by compressedair. Odor control methods have been described by S. Barrington and K. ElMoueddeb, “Zeolite to Control Swine Manure Odours and NitrogenVolatilization”, in: New Knowledge in Livestock Odor Solutions,International Livestock Odor Conference '95, pp. 65-68, and S.Piccinini, Application of a Phillipsite Rich Zeolite During theComposting of Solid Fractions of Pig Slurry, Materials Engineering, Vol.5 no. 2 (1994), pp. 375-81.

[0022] Methods for treating wastewater have been disclosed in referencesthat include the following patents and articles.

[0023] U.S. Pat. No. 5,545,326 describes a pressurized process for thetreatment of high-solids wastewater having relatively high BOD andphosphorous concentration that includes anaerobic and aerobic treatment.The treated wastewater effluent is discharged in an environmentally safemanner such that the residue BOD and phosphorous are concentrated in thesolid fraction which maybe a source of protein. U.S. Pat. No. 5,266,201describes a process for the purification of aqueous solutions pollutedby nitrate ions, such as municipal wastewater, factory effluents, andliquid manure.

[0024] U.S. Pat. No. 4,872,993 discloses processes and techniques fortreating wastewater to remove organic matter and heavy metals. In thetreatment, clay and flocculating agent are added to the wastewater tocause separation of a sludge. Research on unsettleable material removalby chemical coagulation and flocculation has been reported by M. Hanna,D. M. Sievers, and J. R. Fischer, “Chemical Coagulation of MethaneProducing Solids from Flushing Wastewaters”, in: Agricultural WasteUtilization and Management, Proceedings of the Fifth Int. Symposium onAgricultural Wastes, Dec. 16-17, 1985, pp. 632-37, and by D. M. Sievers,Rapid Mixing Influences on Chemical Coagulation of Manures, BiologicalWastes, Vol. 28 (1989), pp. 103-14.

[0025] U.S. Pat. No. 4,519,831 descnies a method of converting sewagesludge solids into dense controlled release, attrition resistantfertilizer agglomerates. The method uses acidic material and uncondensedliquid ureaform U.S. Pat. No. 4,245,396 discloses a process for dryingand granulating sewage sludge either mechanically or by application ofheat. This patent is related to U.S. Pat. No. 4,193,206 on processes fordrying sewage sludge and filtering water, and to U.S. Pat. No. 4,128,946on a drying organic waste process.

[0026] European Patent Application No. 83830277.6 discloses a method forremoving and recovering ammonium, potassium and phosphate ions fromwastewater by selective nutrient removal using ion-exchange resins,resin regeneration and recovery of nutrients and precipitation ofhydrous MgNH₄PO₄ and/or MgKPO₄. This is a RIM-NUT process, where RIM-NUTstands for “removal of nutrients.” This process has also been disclosedin other publications, such as L. Liberti, A. Lopez, V. Amicarelli, andG. Boghetich, “Ammonium and Phosphorous Removal from Wastewater UsingClinoptilolite: A Review of the RIM-NUT Process”, in: Natural Zeolites'93, pp. 351-62; S. J. Kang, T. W. King, P. J. Horvatin, A. Lopez, L.Liberti, and L. Beebe, Nutrient Removal and Recovery from MunicipalWastewater by Selective Ion Exchange, and L. Liberti and A. Lopez,“Applications of a New Physicochemical Method for Removal and Recoveryof Nutrients from Wastewater”, in: Nutrient Removal from Wastewater,edited by N. J. Horan, P. Lowe, and E. I. Stentiford (1994), pp. 371-78.The formation of magnesium ammonium phosphate hexahydrate (struvite) hasbeen studied by C. Maqueda, J.L. Perez Rodriguez, and J. Lebrato, Studyof Struvite Precipitation in Anaerobic Digesters, Water Research Vol. 28(1994), pp. 411-16, and by K. M. Webb and G. E. Ho, Struvite(MgNH₄PO₄.6H₂O) Solubility and its Application to a Piggery EffluentProblem, Water Science and Technology Vol. 26 (1992), pp. 2229-32. Theprecipitation of phosphate and ammonia and nutrient removal from swinewastewater has been studied by E. Brione, G. Martin, and J. Morvan,“Non-Destructive Technique for Elimination of Nutrients from PigManure”, in: Nutrient Removal from Wastewater, edited by N. J. Horan, P.Lowe and E. I. Stentiford, (Technomic Pub., 1994) pp. 33-37; P. H. Liao,Y. Gao, and K. V. Lo, Chemical Precipitation of Phosphate and Ammoniafrom Swine Wastewater, Biomass and Bioenergy, Vol. 4 no. 5(1993), pp.365-71, and by Y. C. Gao, P. H. Liao, and K. V. Lo, Chemical Treatmentof Swine Wastewater, Journal of Environmental Science and Health, Vol.A28 no. 4 (1993), pp. 795-807.

[0027] Fertilizer compositions and/or fertilizer components have beendisclosed in references that include the following patents.

[0028] U.S. Pat. No. 5,549,730 relates to a compression molded tabletfertilizer capable of slowly releasing active ingredients and issuitable for use in horticulture and afforestation, and a method for theproduction thereof

[0029] U.S. Pat. No. 4,845,888 describes a multilayer degradable andcontrolled release multinutrient mulch film, and a process of preparingit. U.S. Pat. No. 4,832,728 reveals fertilizer compositions, processesof making them, and processes of using them. This patent is a divisionof U.S. Pat. No. 4,560,400 that relates to a fertilizer in granularform, and processes for making and using it. U.S. Pat. No. 4,743,287discloses a fertilizer and a method for making a complex humic acidfertilizer by mixing a select organic material, water, and measuredamounts of major inorganic elements of nitrogen, phosphate, potash andsulfur.

[0030] U.S. Pat. No. 5,433,766 reveals a synthetic apatite containingagronutrients and a method for making the apatite. The apatite comprisescrystalline calcium phosphate having agronutrients dispersed in thecrystalline structure, and it can optionally comprise a carbonate and/orsilicon solubility control agent. The agronutrients are released slowlyas the apatite dissolves. U.S. Pat. No. 5,055,124 reveals the productionof potassium phosphate useful as a low-chloride content fertilizer byreacting phosphoric acid, commercial or technical grade, withfertilizer-grade potassium chloride. The reaction product is used toproduce various types as well as grades of fertilizers.

[0031] Methods that include fermentation or the use of certainmicroorganisms have been disclosed in references that include thefollowing patents.

[0032] U.S. Pat. No. 5,118,336 discloses a method for valorizing liquidmanure from pigs by elaboration of biological amendments. The methodincludes fermentation of a biomass based on a mixture of pig liquidmanure and a carbonaceous medium. U.S. Pat. No. 4,795,711 describes thefermentation of organic materials for producing heat and fertilizer.U.S. Pat. No. 5,093,262 discloses a method and apparatus for producingorganic fertilizer with the use of nitrogen fixing bacilli.

[0033] Other treatments, production methods or compositions that relateto organic wastes have been disclosed in references that include thefollowing patents.

[0034] U.S. Pat. No. 5,087,474 particularly relates to a method ofrecovering particulate ainl feed fats, free of malodors and pathogensfrom abatoir by-products and to the product recovered by this method.

[0035] U.S. Pat. No. 4,765,900 describes a method for treating organicwaste, which includes separating the liquid portion of the waste fromthe solid portion prior to reacting the solid portion in an acceleratedwet oxidation reaction. U.S. Pat. No. 4,278,699 describes a method ofpurifying distillers solubles and use of the purified matter.

[0036] U.S. Pat. No. 4,310,552 discloses a swine, hog and pig fodderwhich comprises the customary digestible meal or grain component incombination with an indigestible blown perlite additive.

[0037] U.S. Pat. No. 4,109,019 is directed to a method for producingfeeds for ruminant animals whereby carbamides, particularly urea andbiuret, are reacted with fermented proteinaceous agricultural productsand wastes with the aid of an aliphatic dicarboxylic acid catalyst toproduce feed which releases protein and protein equivalent nitrogen in aslow and controlled manner in the rumen.

[0038] U.S. Pat. No. 4,176,090 describes interlayered clay compositionsused as catalysts, catalytic supports, and sorbents.

[0039] Despite the plurality of methods for treating organic waste andfor producing fertilizer, conventional methods leave unsolved problems.This is particularly the case regarding strategies that rely onencompassing and integrating organic waste treatment methods andfertilizer production processes for making fertilizer with desiredenvironmental and agronomical properties. More specifically, there is aneed for commercially successful organic waste treatment and fertilizerproduction processes.

[0040] The composition of animal waste depends on both the kind ofanimal and the way the waste is handled. Poultry operations generallyproduce dry waste, with about 15%-25% moisture whereas hogs and cattlegenerate waste that is more liquid. In addition, water is typically usedto flush hog and cattle waste out of barns and into storage facilities,thus producing a slurry that can be up to 97% liquid and it is typicallystored either in earthen lagoons or in slurry tanks. In theseconventional treatments, “many of the solids (including much of thephosphorous) settle into a sludge at the bottom. Most nitrogen remainsdissolved in the water or volatilizes into the atmosphere. A fanner whoutilizes the animal waste for nutrients pumps the liquid out fornutrients or irrigation, and may agitate the sludge at pumping time tocapture the nutrients that otherwise would remain behind.” Animal WastePollution in America: An Emerging National Problem, Environmental Risksof Livestock & Poultry Production, Report Compiled by the Minority Staffof the US Senate Committee on Agriculture, Nutrition, & Forestry forSen. Tom Harkin, December 1997.

[0041] Most methods that rely on conventional lagoons do not clarity theeffluent that carries the organic waste prior to its accumulation in thelagoon system. This practice leads to unnecessarily high loading of thelagoon system, thus requiring large conventional lagoons. Whereas somerecently introduced lagoon treatments claim to reduce odors, thesetreatments essentially increase greenhouse gas emissions, such as carbondioxide and ammonia gas emissions.

[0042] In anaerobic lagoons, one of the more common methods of hogmanure treatment, organic matter in the waste is decomposed by bacteria.These lagoons are under increased criticism for the offensive odor thatresults from incomplete decomposition and ground water contamination.Anaerobic lagoons also diminish nutrient value in the hog wastes throughprocesses that include the loss during digestion of much of the nitrogenin the waste.

[0043] The removal of eutrophic ions from wastewater and thereintroduction of nitrogen and phosphorus into the environment is thefocus of some methods that nevertheless do not address the recovery ofbiogas that has considerable energetic value and whose release into theatmosphere can have a serious impact on air quality, ozoneconcentration, and global climate changes. In addition, recovered biogascan be used for heating or electric energy generation. Whereas thecapture of the gases released in the conversion of organic waste tofertilizer leads to a reduction or elimination of undesirable odors,greenhouse gas emissions, and gases that can contribute to aciddeposition, some methods that focus on the elimination of odors orpathogenic content of organic waste do not provide for the conversion ofwaste into a commercial fertilizer.

[0044] After biogas recovery, the sludge that can be separated from theorganic waste effluent contains ammonia and phosphates that arerecoverable by precipitation under controlled pH conditions. Thedensified precipitate is a fertilizer that can be supplemented withother compounds to incorporate in its composition micronutrients and tostandardize its composition, but most organic waste treatments neglectthe incorporation of these complements that are necessary for plantgrowth, and more specifically, for crop production.

[0045] Furthermore, the conversion of waste into fertilizer in mostconventional organic waste treatments does not absorb residues producedby other activities. These residues include the waste generated by, forexample, industrial mining and the combustion of coal in power plants.

[0046] It is also important that the reintroduction of phosphates andammonia into the environment be achieved by means of a slow releasefertilizer. Certain components in organic waste used as a source ofplant nutrients far exceed plant demand when they are not properlyadministered. For example, it is acknowledged that phosphorousnonpoint-source pollution is becoming a problem throughout the USA. F.Liu, et al., Phosphorous Recovery in Surface Runoff from Swine LagoonEffluent by Overland Flow, J. Environmental Quality Vol. 26 (1997)995-1001. In addition, ammonia is usually released from untreated pigslurry that is directly applied as a fertilizer. Ammonia loss rates havebeen reported as being very high during the first 4 hours to 6 hoursafter slurry application. These ammonia losses can be significantlyenhanced by temperature and wind speed increases. Sven G. Sommer, etal., Ammonia Volatilization from Pig Slurry Applied with Trail Hoses orBroadspread to Winter Wheat: Effects of Crop Developmental Stage,Microclimate, and Leaf Ammonia Absorption, J. Environmental Quality Vol.26 (1997) 1153-1160. In contrast with some processed organic waste, theslow release fertilizer produced according to this inventionconsiderably decreases water pollution that would otherwise take placeby leaching.

[0047] Finally, some methods produce variable composition fertilizersdepending on the characteristics of the feed provided to the animalsthat produce the waste, thus supplying non-standard compositionfertilizers. It would be desirable to produce a fertilizer of standardcomposition that can be appropriately modified to satisfy the needs ofdifferent agribusiness.

[0048] Currently, organic waste is largely treated and disposed of byrelying on technology developed in the 1940's for small scaleoperations, and integrated waste systems are nonexistent. In particular,most of the presently available waste treatment and disposal methodologyrelies on single unit operations which address a single problem or avery reduced number of problems. This approach cannot solve the varietyof environmental, economical, operational, and technological problemsthat the multifaceted waste treatment and fertilizer production industryfaces.

[0049] Descriptions of methods that address specific elements of themore encompassing problem of converting waste into useful fertilizer byan economical and nonpolluting process can be found in some of theafore-mentioned related art. Some of these methods necessitate theaddition of materials such as caustic products, urea or formaldehyde.Others rely on sources of energy for heating or for oxygenating byforced air flow.

[0050] For example, the treatment of organic waste with causticchemicals may eliminate the waste's pathogenic content and render itsuitable for its use in agriculture, but this method would not solveother problems such as the prevention of emissions of acrid odors andother gases that contribute to the greenhouse effect and to thedepletion of ozone. In particular, some conventional methods aim ateliminating nitrogen compounds from the organic waste, but in doing sothey also increase greenhouse gas and acrid gas emissions. In addition,these methods decrease the yield of nitrogen compounds in the finalproduct into which the organic waste is processed. Such methods wouldnot absorb other residues and waste that would have to be independentlydisposed of They would not produce useful fuel material, and wouldrequire large processing facilities.

[0051] Another limitation faced by most conventional waste treatmentmethods is the inability to effectively treat large amounts of organicwaste. This limitation becomes particularly relevant in a productionframework in which large animal operations gain efficiency by raising avery large number of animals in controlled indoor environments which inturn produce enormous amounts of organic waste. See, for example, WarrenCohen, United States Deep In Manure, US News & World Report, Jan. 12,1998, p. 46.

[0052] Modern farming operations must address the problems that areinherent to the confining of large numbers of animals in concentratedfeeding operations. To this respect, it has been reported that moremanure is produced in some areas of the US than can be safely applied toavailable crop land. See, for example, National Legislation Needed toAddress Animal Waste Pollution, Senate Panel Told, BNA EnvironmentReporter, Vol. 28(49) (1998) pp. 2647-49, and Waste From Hog, ChickenFarms Growing at ‘Alanning’ Rate, Group Says, BNA Environment Reporter,Vol. 28(48) (1998) pp. 2648-50.

[0053] Sewage waste water treatment faces some of the same problems andraises similar concerns. Whereas the US has been regarded as a leader insewage management, and sewage-treatment technology has been described asa success story in 20th-century US, it has been asserted thatsignificant commercial advantages have been significantly lacking in thepast few decades. Moreover, existing treatment methods have beencharacterized as facing a number of inherent problems that must beovercome to make further progress in the next century. William J.Jewell, Resource-Recovery Wastewater Treatment, American Scientist Vol.82 (1994) pp. 366-75.

[0054] Attempts in the industry to overcome the multifarious limitationsthat are inherent to single unit operations have failed to date becauseof the inability to implement them economically or because ofoperational and technical difficulties. This limited scope of thecurrent waste treatment and disposal technology has lead to industryproblems that have received intense scrutiny by the media. Therefore, anencompassing, integrated waste treatment system is a long felt, yetunsatisfied, need in this industrial sector. The need for anencompassing and integrated waste treatment system has been expressed ina plurality of articles, statements on public health impacts and studiesand regulations on animal feeding operations.

[0055] The EPA and legislators have been increasingly sensitive to theproblems caused by current organic waste disposal practices and theyhave been focusing on the need to address such problems. In particular,the development of scientifically valid limits on land application ofmanure has been called, and the EPA has been reported as planning torevise the feedlot effluent limitations guidelines for poultry and swineby 2001, and for beef and dairy cattle by 2002. See Federal Role inAnimal Waste Control Should Be Limited, House Panel Told, BNAEnvironment Reporter, Vol. 29(3) (1998) pp. 178-79; Draft Strategy forAnimal Feeding Operations, EPA Memorandum, Mar. 4, 1998, and ComplianceAssurance Implementation Plan For Concentrated Animal FeedingOperations, Office of Enforcement and Compliance Assurance, EPA, Mar. 5,1998.

[0056] Acridity problems have also been increasingly addressed bylegislators and government agencies. For example, following arecommendation from the Missouri Department of Natural Resources, theState of Missouri Air Conservation Commission reportedly agreed on Feb.3, 1998, to form a task force to analyze odor pollution issues relatedto large hog and poultry farms in the state. See Task Force to StudyOdor Issues Relating to Large Hog, Poultry Farms, in BNA EnvironmentReporter, Vol. 28(40) (1998) p. 2134.

[0057] In addition to the focus on the problems that untreated organicwaste discharge may cause, government strategies have also highlightedthe need for developing new technological approaches for treatingorganic waste, pointing out in particular that the use of successful andinnovative technological approaches should be encouraged and pursued.Draft of the Strategy for Addressing Environmental and Public HealthImpacts From Animal Feeding Operations, EPA, March 1998, pp. 11-12.

[0058] Each of the afore-mentioned patents and elements of related artis hereby incorporated by reference in its entirety for the materialdisclosed therein.

SUMMARY AND OBJECTS OF THE INVENTION

[0059] It is desirable to dispose of organic waste that would otherwisepose a serious environmental problem Instead of its mere disposal, it isdesirable to treat the organic waste and convert it into usefulproducts. This conversion process however, should not lead to otherforms of pollution. Instead, the conversion process should optimallyrely on methods that are not very energy demanding and that do notrequire the consumption of other substances of complex, expensive, orpolluting manufacture. Conversion of organic waste to fertilizer andoptionally to feed supplement, and biogas recovery are two desirable andbeneficial activities that can make the waste treatment processeconomical. In addition, these activities can make of the wastetreatment process a practical and effective alternative toenvironmentally impermissible disposal.

[0060] To achieve the desirable goal of eliminating water pollution,organic waste treatment must provide effluents in every separation andreaction step that meet EPA discharge standards. The accomplishment ofthis goal should be further complemented by the capture and effectiveuse of gases that, if released from the organic waste, would contributeto acid deposition, ozone depletion, greenhouse effect, and whoseacridity could be intolerable.

[0061] It is also desirable that the organic waste treatment products donot contribute to water pollution by leaching and that they becomeeconomical slow release commercial fertilizer. Finally, it is alsodesirable that the organic waste treatment process be carried out byimplementing techniques and methods that lead to a minimization of theoverall land surface dedicated to the entire organic waste conversionprocess.

[0062] The expression “organic waste” is used herein as a descriptiveterm that encompasses waste of organic origin whether in the form ofeffluent, solid, sludge, slurry, or any other form that can be producedin organic waste sources. Furthermore, it is an operation well known tothose skilled in the art to convert waste in, say, solid form toeffluent by flushing the solid waste with water, if such conversion wereneeded at any step in the organic waste treatment and conversion processthat is described and claimed below.

[0063] The objectives of this invention include the following. Thegeneral objective is to provide a method for the treatment of organicwaste, whereby the organic waste is converted into commercialfertilizer, biogas useful for heating and power generation, and finaleffluents that can be directly employed in irrigation and wetlandprojects. In particular, the organic waste to be treated according tothe methods of this invention can be, for example, hog farm effluent andsolid matter, cattle or poultry waste.

[0064] It is a further objective of this invention to provide a methodfor the treatment of organic waste and production of supplement feed foranimals, including cattle feed quality products.

[0065] Whether this invention is characterized as providing a method forproducing fertilizer or for producing fertilizer and feed supplement,these characterizations are merely concise references to anotherobjective of this invention that consists of providing a method forproducing fertilizer only, feed supplement only, or both fertilizer andfeed supplement.

[0066] It is a further objective of this invention to significantlyreduce or even eliminate the release of gases that can lead to acridodors, loss of potential plant nutrients, and environmentallyundesirable emissions of gases that may contribute to acid deposition,ozone depletion and an overall insalubrity of local farmingenvironments. This reduction or even elimination of released gases canbe achieved in this invention by employing gas adsorbing substances, inparticular ammonia adsorbing zeolites, at several stages of the wastegeneration and/or waste treatment processes, by reacting ammonia withacids, such as phosphoric or sulfuric acid, and by recoveringmethane-rich biogas.

[0067] The utilization of gas-adsorbing substances such as zeolitesaccording to this invention minimizes the emission of ammonia gas fromthe animals' gastrointestinal tracks and from the organic waste itself.The biogas can be directly used in the integrated waste treatment andfertilizer and feed supplement production processes and/or it can beused in organic waste sources in operations such as drying manurefiltrate. Furthermore, this biogas can be used for heating, powergeneration, or in subsequent synthetic or catalytic processes. Theprevention of gas releases from organic waste sources leads to theadditional advantage of satisfying the public demand for acrid odorreduction in, or even its elimination from, organic waste sources.

[0068] The minimization or reduction of gas emissions by this inventionis further facilitated by the reliance on either no lagoons or onreduced-size lagoons. When this invention relies on reduced-sizelagoons, gas emissions from such lagoons are reduced or eliminatedbecause this invention reduces anaerobic lagoon loading and lagoonsurface area by comparison to loading and surface area of conventionallagoons. Reliance on reduced-size small load lagoons makes anaerobiclagoons economically feasible and extends the lagoon useful life withrespect to that of large conventional lagoons. Furthermore, it leads toan increase in the available surface area of useful space at the organicwaste treatment site and to a minimization or elimination of the risk ofwater contamination by spills or leaks that are more difficult tocontrol in large, big-load conventional lagoons. Because this inventiondoes not rely on conventional biological and volume reduction treatmentsin anaerobic lagoons, biogas emission from conventional lagoons iseliminated.

[0069] It is a further objective of this invention to provide a wastetreatment process in which the separation of solids is accomplished withvery high settling rates. Accordingly, the liquid-solid separation ofthe organic waste is improved with respect to that achieved by mostconventional organic waste treatment processes. Furthermore, theeffluents separated from the organic waste according to this inventioncan be used in irrigation and wetland projects under current EPAdischarge standards and salting problems in recycling streams areeliminated. The separation process of this invention can also be used toremove undesirable components from municipal sludge.

[0070] One of the features of this invention is that the treatment oforganic waste can be accomplished by using waste materials from othersources, such as mining waste and fly ash. This feature leads to a moreadvantageous and effective waste treatment because mining waste and flyash would otherwise generate disposal problems.

[0071] It is a further objective of this invention to convert organicwaste into an organic-based standard composition, granular, slowrelease, readily available fertilizer with micronutrients whose deliveryrequires no changes in existing fertilizer delivery systems. Morespecifically, one of the objectives of this invention is to manufactureand provide a nitrogenphosphorous-potassium (hereinafter “NPK”)fertilizer with sizing materials and, in particular, with zeolite anddensifiers. One of the fertilizers produced according to this inventionis made from hog waste, zeolite, fly ash, lime, and optionally, offgrade commercial fertilizers. In general, the raw ingredients for thefertilizer and food supplement production methods of this invention areeconomical and the production equipment size is not limited by processengineering.

[0072] The fertilizer production methods of this invention are flexibleenough as to produce fertilizer products that combine high availabilityof plant nutrients, slow release characteristics, soil amendmentproperties, low salinity, and a rich mix of micronutrients in theorganic base. Because of the flexibility of the fertilizer productionmethod of this invention, the fertilizer composition can beadvantageously tailored to the demands of specific markets.

[0073] The waste treatment and fertilizer and food supplement productionmethods of this invention rely on a variety of mechanical processingequipment that includes processing equipment for efficiently densifyingorganic waste. This feature leads to the advantageous improvement of theorganic waste handling characteristics and facilitates the retention ofzeolites, magnesium, phosphates and ammonia in the organic wastethroughout the process, thus becoming part of a finished fertilizer.

[0074] A feature of the mechanical processing equipment of thisinvention is that it can operate in either continuous or batch mode.Accordingly, an advantage of the organic waste treatment and fertilizerand feed supplement production methods of this invention is that theycan be implemented in small farms as well as in large farms, batchoperations being more useful for small farms and continuous operationsbeing more useful for large farms.

[0075] It is a further objective of this invention to provide organicwaste treatment and fertilizer and food supplement production methodsthat can absorb the organic waste production from a great diversity oforganic waste sources, whether the organic waste sources are small orlarge scale operations, and regardless of whether the organic waste isproduced at the organic waste treatment site or at a plurality of nearor remote organic waste sources. A feature of the methods of thisinvention is that their implementation is versatile enough as to beadaptable to different economic strategies and needs, whether it is inorganic waste sources that are being built or in already existingorganic waste sources by simple retrofitting. With this versatility, anadvantage of the methods of this invention is that they can easily beimplemented for reclaiming existing sites that are destined to eitherclosure or cleanup.

[0076] When implemented in conjunction with farms or livestockoperations, the integrated waste treatment and fertilizer and foodsupplement production methods of this invention successfully density anddry manure slurry, significantly improve animal health, feedingefficiency and reproductive capacity, and they lead to the production ofan economically competitive organic-based slow release fertilizer andoptionally, to the production of feed supplements. These features permitto advantageously improve the overall economics of livestock productionby improving animal health, decrease waste management costs, implementprocesses that easily comply with environmental regulations, reduce longterm liability by reducing or eliminating water and soil contamination,and use waste material to profitably produce NPK fertilizer andoptionally feed supplements.

[0077] The objectives of this invention are specially significant to thepork producing sector of the US and most countries. The biggest concernsof pork producers include: Competition for land space between farms andurban development, environmental problems, competitive marketing ofproducts, and proper care of animal diseases and animal health. Becausethe present invention significantly reduces the size of conventionallagoons, or even eliminates the need for lagoons, its embodiments needmuch less surface area than that required by conventional methods.

[0078] The positive environmental effects of the present invention aremanifest in three forms: The minimization, or even elimination, ofemission of gases that would otherwise have detrimental environmentaleffects and would be a nuisance to human beings; the recovery ofenergy-rich gases whose subsequent utilization reduces reliance on otherforms of energy, and the discharge of effluents with reduced nutrientloading. Reduction of nutrient loading in final effluents can largelyeliminate nutrient accumulation problems when the effluents are used forirrigation or when the effluents are used to make constructed wetlandseconomically viable.

[0079] The effects of this invention on marketing pork products includethe ability to raise animals in less remote areas because of itsenvironmentally friendly waste treatment method, the production of lowcost high-quality fertilizer, and the optional production of feedsupplement that lead to a reduction of the operational costs.Furthermore, animal diseases are reduced and animal health is improvedbecause of the improved conditions in barn air quality.

[0080] The objectives of this invention are achieved by means of anintegrated waste treatment method that relies on modern technology andthat can be used in operations that range from small scale to largescale operations. In particular, the objectives of this invention areachieved by a specially designed mechanical system which facilitates theimplementation of a method for separating organic waste into a liquidand a precipitate. The precipitate includes the products of reacting theorganic waste with flocculent, phosphate precipitating agent, ammoniaretaining agent, base and optionally a densifier.

[0081] Optionally, gas reactors recover methane-rich biogas that can beused in heating, power generation, or subsequent synthetic or catalyticprocesses.

[0082] The liquid, optionally treated in a reduced load lagoon system,can subsequently be used in irrigation, wetland projects, or recycled inthe organic waste source. The precipitate yields a solid fertilizer basewhich can be used as such as a fertilizer or it can be mixed with othercompounds such as nitrogen, potassium, or phosphorous containingcompounds as well as micronutrients to improve its grade as afertilizer.

[0083] Subsequent steps include pelletizing and drying the mixture andcontrolling its size to obtain standard size fertilizer pellets. Thefinal product is an organic-based, granular, slow release fertilizerwhose composition includes micronutrients. This fertilizer is readilyavailable to plants and it can have a standard composition and grainsize. The solid obtained from the filtration of the solid fraction canbe adjusted to a proper pH, if needed, and used as a feed supplement.

[0084] Whether this invention is implemented for the production offertilizer, feed supplement, or both, one of the objectives of thisinvention is nitrogen conservation. To conserve nitrogen, this inventionpreferably relies on the addition of zeolite, optimally an ammoniaadsorbing zeolite, to one or several of the different organic wastegeneration steps. For example, zeolite can be added to animal feed, itcan be incorporated into farm waste streams, and/or used in the wastetreatment process itself Added zeolite retains nitrogen which wouldotherwise be released mostly in the form of gaseous ammonia. Thenitrogen retention achieved by the method of this invention contrastswith traditional waste treatment methods which allow for a significantrelease of ammonia. In these traditional operations, release of ammoniamay account for a significant loss of the nitrogen initially containedin the organic waste, an ammonia loss that can be about 70%.Furthermore, the capture of ammonia can be increased according to themethods of this invention by reacting ammonia with acids such assulfuric and phosphoric acids.

[0085] Additional objects, features and advantages of this inventionwill become apparent to persons of ordinary skill in the art uponreading the remainder of the specification and appended claims and uponreferring to the attached Figures, or may be learned by the practice ofthe invention as set forth hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0086] In order that the manner in which the above-recited and otheradvantages and objects of the invention are obtained, a more particulardescription of the invention briefly described above will be rendered byreference to a specific embodiment thereof which is illustrated in theappended drawings. Understanding that these drawings depict only atypical embodiment of the invention and are not therefore to beconsidered to be limiting of its scope, the invention will be describedand explained with additional specificity and detail through the use ofthe accompanying drawings in which:

[0087]FIG. 1 shows a block diagram of the main steps of an exemplaryembodiment of the organic waste treatment and commercial fertilizerproduction process of the invention.

[0088]FIG. 2 shows a block diagram of the main steps of anotherexemplary embodiment of this invention in one of its possibleapplications to the treatment of waste generated in hog barns.

[0089]FIG. 3 shows a block diagram of the main steps of anotherexemplary embodiment of this invention as applied to the treatment withno lagoons of farm organic waste, and its transformation into an organicbase that is further utilized as fertilizer or as feed supplement.

[0090]FIG. 4 shows a partial matter flow diagram of an exemplaryembodiment of an organic waste treatment and fertilizer productionplant.

[0091]FIG. 5 shows a partial matter flow diagram of another exemplaryembodiment of an organic waste treatment and fertilizer productionplant.

[0092]FIG. 6 shows a partial matter flow diagram of an exemplaryembodiment of an organic waste treatment and fertilizer production plantthat includes features for capturing in the form of ammonium salts theammonia that would otherwise be released into the atmosphere.

[0093]FIG. 7 schematically shows an ammonium sulfate crystallizer.

[0094]FIG. 8 shows a graph of the weight percentages of ammonia gas andammonium ions in an aqueous solution as a function of the medium pH atthree temperatures.

[0095]FIG. 9 shows a partial matter flow diagram of an exemplaryembodiment of a dryer/pelletizing unit for an organic waste treatmentand fertilizer production plant.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0096] The illustrative embodiments of the invention exemplify theapplication of the useful characteristics discussed below, and furtherreference to these and other useful and novel features is made in thefollowing discussion of each illustrative embodiment. One embodiment ofthe organic waste treatment and fertilizer production process isrepresented by the block diagram in FIG. 1. This and other exemplaryembodiments are intended to limit neither the scope of the processes northe apparatuses or materials that are needed for performing theprocesses.

[0097] Referring to FIG. 1, organic waste 102 produced at an organicwaste source that in particular can be farms 101 is clarified inclarifier 103. In particular, this organic waste source can be pigfarms, but the process steps shown in FIG. 1 are not limited only to thetreatment of organic waste produced in pig farms.

[0098] The clarification in clarifier 103 can be effectivelyaccomplished by treating the organic waste with a flocculant.Flocculants, whether alone or in mixtures, include inorganic compoundssuch as iron and aluminum compounds, whether solid or in solution, lime,which is sometimes used as a coflocculant, and organic products such aschitosan and other natural products including starch, guar gum andprotein colloid such as gelatin and animal glue. Examples of preferrediron and aluminum compounds used as flocculants include aluminumsulfate, iron (III) chloride, and iron (II) sulfate. One of the benefitsof using lime is that some of the bases in it, such as calciumhydroxide, eliminate pathogens in the organic waste. In the context ofthis invention, lime generically describes bases that include calciumcompounds, whether in the form of oxides, hydroxides or carbonated,mixtures thereof, and it might contain similar compounds, the mostcommon of which are the corresponding magnesium-based compounds.Depending on the organic waste source location and the type ofactivities developed therein, preferred flocculants can typically beobtained at or near farm sites from natural sources, in which case theiruse leads to considerable cost reduction. They can also be obtainedcommercially, together with synthetic organic flocculants that areusually polymeric materials. Synthetic organic flocculants can beanionic, cationic and nonionic, and they are useful when theflocculating conditions impose some operational restrictions such as pHsensitivity or resistance to some chemicals. Cationic polyacrylamideemulsions are preferred in the methods of this invention as flocculants.Among cationic flocculants such as those marketed with the designationsNALCO7191, NALCO7193, NALCO7194, NALCO7196, CYTEC2085, and CHEMAX2746,the flocculants NALCO7191 and NALCO 7193 are preferred, with NALCO7191being more preferred. The preferred flocculants in this invention arepreferably used in emulsions at concentrations of about 1 μg/l.

[0099] Two products are extracted from clarifier 103: primary sludge 104and overflow liquor 105. In this context, the terms clarification,sedimentation, coagulation, and flocculation are used synonymously tosignify the separation of material that in the absence of the indicatedtreatment would remain in the liquid phase. For example, a significantamount of the material in primary sludge 104 that is separated inclarifier 103 would remain in the overflow liquor 105, also calledliquid waste, in the absence of clarification in clarifier 103. Thenon-liquid material in clarifier 103 includes settleable andnonsettleable substances and it becomes part of primary sludge 104.Nonsettleable material comprises material that would take a very longtime to settle and material that would not settle in the absence of aflocculent or an agent that induces the formation of nucleation centers.Suspended solids in the organic waste are an example of settleablematerial, and organic matter in colloidal form in the waste is anexample of nonsettleable material.

[0100] The separation of primary sludge 104 from overflow liquor 105 canbe accomplished by methods such as industrial vacuum filtration, bymeans of devices such as a screw press or a belt press, or by combiningthese and other methods and devices that are conventionally used insimilar separation processes. The use of clarifier 103 increases theamount of solid material in primary sludge 104 from 20% to 50% solidscompared to a system without a clarifier. This increased recovery ofsolid material is accomplished in the present invention becausenonsettleable, in addition to settleable, material is separated inclarifier 103. This solid material is rich in nitrogen, phosphorous andit would lead to biogas emissions if it were discharged with theoverflow liquid 105 into anaerobic lagoons 108.

[0101] Primary sludge 104 is transported by sewer lines and/or motorizedmeans of transportation 106 to gas reactors 107 in a processing plant.The extensive separation achieved in clarifier 103 plus the suitablemeans of transportation 106 permit the implementation of the wastetreatment and fertilizer production process of this invention at anyconvenient location, whether such location is the organic waste sourcesite itself or another site away from the organic waste source. Thisversatility is indicated in FIG. 1 by a horizontal dash line thatdivides the block diagram into an upper part and a lower part. The upperpart of the diagram schematically describes processes that can takeplace at the organic waste source site itself. The lower part of thediagram schematically describes processes that can take place either atthe organic waste source site or at another location such as a near orremote processing plant location.

[0102] Overflow liquor 105 is delivered to anaerobic lagoons 108.Because a high fraction of the material in organic waste 102 isseparated as primary sludge 104 in clarifier 103, and only the overflowliquor 105 is fed to lagoons 108, loading of these lagoons 108 isconsiderably less than the loading that they would withstand in acurrent state-of-the-art process with no clarifier. According toconventional disposal methods, organic waste is delivered from organicwaste sources 101 directly to the conventional counterpart of anaerobiclagoons 108, which are in effect natural digesters that produce biogasthat is usually released into the atmosphere. In contrast, clarifier 103permits the separation of an overflow liquor 105 that is mostly free ofsolids, colloids, methane, and acrid gases. Equivalently, theembodiments of this invention permit the efficient recovery of biogasesfrom primary sludge 104 that is obtained from clarifier 103, whereasconventional state-of-the-art processes release biogases into theatmosphere or less efficiently recover them.

[0103] Anaerobic lagoons 108 usually include a system of primary lagoonswhere a mostly biological treatment occurs, and a system of secondarylagoons where the volume of liquor is reduced. Means of carrying out thebiological treatment include anaerobic digestion. Liquor volumereduction in the system of secondary lagoons can be accomplished byprocesses such as evaporation, use of gray water for irrigation orfertilization of crops, and support of constructed wetlands. In essence,the treatments in anaerobic lagoons 108 are such that the productsdischarged from these lagoons meet sewer conservation service standards.The diminished load of anaerobic lagoons 108 allows lagoons that are 60%smaller than the corresponding anaerobic lagoons used in currentstate-of-the-art methods.

[0104] The liquor treated in anaerobic lagoons 108, concisely “theanaerobic effluent”, can be evaporated or used in irrigation or wetlandprojects 109 and it can also be reused at farms 101, and more generallyin organic waste sources. For example, the anaerobic effluent can berecycled as treated pit recharge 110 which is used for flushing. Asindicated above, while clarifier 103 and anaerobic lagoons 108 arepreferably built and operated at the same site where organic wastesources 101 are located, the rest of the constituent elements of theprocess, starting by gas reactors 107, can be built and operated at theorganic waste source sites or at some other convenient location.

[0105] Methane-rich biogas 111 is separated in gas reactors 107 fromprirnary sludge 104 to produce degasified sludge 115. Although theamount and composition of the biogas recovered depends on a variety offactors such as the type of farm animals and the feed supplied to them,biogas with a heat of combustion of about 2.2·10⁴-2.6·10⁴ kJ/m³, (about5.4·10³-6.2·10³ kcal/m³ or about 600-700 Btu/ft³) may typically berecovered from gas reactors 107. The composition of this biogas ismostly methane and carbon dioxide, and it is recovered from gas reactors107 in an amount of about 0.4 m³/(h·100 animals), (about 14 ft³/(h·100animals)).

[0106] In contrast, the heat of combustion and the amount of biogasrecovered by current state-of-the-art methods in facilities holdingsimilar animals under similar conditions are comparable to thecorresponding parameters for existing digesters, if biogas is recoveredat all. For example, the report by L. M. Safley, Jr., et al., LowTemperature Lagoon Digester for Biogas Production from Swine Manure,FIG. 18, and summary, pp. 12-13, shows that the biogas production in aconventional low temperature lagoon digester at a facility holding 11494pigs did not exceed about 0.12 m³/(h·100 animals), (about 4.2 ft³/(h·100animals)) and some measurements indicate that practically no biogas wasrecovered some days. Furthermore, the biogas production fluctuatedconsiderably between 0 and about 0.12 m³/(h·100 animals), (0 and about4.2 ft³/(h·100 animals)). These fluctuations were observed when theaverage lagoon temperatures changed in an interval of about 7.2° C.(about 13° F.), from about 10° C. (about 50° F.) to about 17.2° C.(about 63° F.). The reported mean biogas production was about 0.054m³/(h·100 animals), (about 1.92 ft³/(h·100 animals)) with a heat ofcombustion of about 3.05104 kJ/m³, (about 7.29·10³ kcal/m³ or about817.6 Btu/ft³). These figures indicate that current state-of-the-artlagoon facilities like the ones considered in the study by L. M. Safley,Jr., et al. (cited above), recover comparatively little biogas.Furthermore, these conventional anaerobic digesters do not focus on thecapture of greenhouse and ozone depleting gases that embodiments of thepresent invention recover, for example, by the separation that takesplace in clarifier 103.

[0107] For exemplary purposes, gas reactor 107 can be implemented as asystem that comprises large, gently stirred, processing vessels. Whetheralone or as part of a more complex mixture, this separated biogas 111can be used for heating 112, electricity generation 113, or otherprocesses such as chemical processes 114 that include synthesis andcatalytic conversion. In particular, thermal and electric energygenerated by combustion of the separated biogas can be used in afertilizer processing plant, farms, or in applications near theprocessing plant where the biogas 111 is produced in reactors 107.

[0108] Degasified sludge 115 from gas reactors 107 contains most of thenitrogen and phosphorous that were initially in organic waste 102. Theamounts of nitrogen and phosphorous in the degasified sludge 115 arerespectively about 200% and 100% greater than the corresponding amountsrecovered according to current state-of-the-art methods because of theway in which primary sludge 104 is separated from organic waste 102, andbecause of the incorporation of zeolites into the feed supplied toanimals in farms 101 or added to the initially generated organic waste.Degasified sludge 115 is subsequently fed into reactors and clarifiers116 together with one or more of the following agents: an ammoniaretaining agent, such as a suitable natural or synthetic zeolite, aprecipitating agent, such as magnesium chloride or a suitable brine, adensifier, such as clay, fly ash, bentonite, crushed limestone, zeolite,perlite and mixtures thereof, and a pH control agent, such as lime.

[0109] The terms “retain”, “retaining” and “retention” are herein usedto refer to retention of a gas or gases by a substance, whether theretention is accomplished by absorption, by adsorption or by acombination of adsorption and absorption. Thus, for example, an “ammoniaretaining agent” stands for a substance that retains ammonia andprevents its escape from the medium as a gas whether the speciespredominantly retained by the ammonia retaining agent is ammonia itselfor ammonium ions.

[0110] The specific reference to magnesium chloride is not limiting, butmerely illustrative. Any other compound such as magnesium sulfate thatprecipitates phosphate as a salt that is a fertilizer or any combinationof such precipitating compounds can be used instead of, or incombination with, magnesium chloride.

[0111] Clinoptilolite, a natural zeolite, is an example of an efficientand preferred ammonia adsorbing zeolite that can be used to treat thesludge that is discharged from the gas reactors. The use of ammoniaadsorbing zeolite in the nutrient recovery process permits the reductionof acrid odors. In addition, odor can be controlled more effectively ifan ammonia adsorbing zeolite is added to the livestock feed. The choiceof preferred zeolites in this invention is also determined by therequired characteristics of the fertilizer that is produced from theorganic waste. For example, K—Ca clinoptilolites are excellent for soilconditioning as opposed to Na clinoptilolites. Other zeolites thatretain ammonia include chabasite and phillipsite. Because naturalsources of zeolites sometimes contain mixtures of zeolites instead ofone single zeolite and some zeolites share several commoncharacteristics, the term “zeolite” in this context will refer to onezeolite and also to a mixture of zeolites with desired properties.Analogously, reference to a specific zeolite by name in the context ofthis specification and appended claims is to be understood as referringto named specific zeolites and also to a mixture of zeolites with thedesired properties in which the specifically named zeolite is asignificant component.

[0112] Fly ash is an example of a densifier that can be used in thetreatment of the same sludge. The pH in this treatment can becontrolled, preferably to a value between about 9 and about 12, morepreferably between about 10 to about 11. A residence time of about twohours in a medium with a pH of about 10.5 leads to significant reductionor almost elimination of the pathogen content of the organic waste beingtreated. A higher pH of about leads to pathogen content elimination in ashorter time period. Consequently, exclusive reliance on the mediumbasicity for pathogen content elimination requires a higher preferred pHvalue of about 12.

[0113] When a base has to be added to control the pH, lime is apreferred base for this purpose. Fly ash can also perform as a total orpartial replacement of lime for controlling the pH in this process step.Furthermore, replacing lime for fly ash may be economically advantageousdepending on the relative availability of these substances.

[0114] Magnesium chloride from brine, fly ash from coal burning powerplants, and lime are explicitly and exemplary referred to in thiscontext because of the availability of these materials in somegeographic locations. Their use in these locations makes the organicwaste treatment and fertilizer and feed supplement production accordingto this invention particularly economical. In addition, the processutilizes fly ash, which is an industrial waste that should otherwise bedisposed of Nevertheless, fly ash is not the only substance that can beused as a densifier. Bentonite, for example, is another product that canbe used as a densifier instead of, or in combination with, fly ash. Thisversatility is important because some industrial sources might producefly ash that is not appropriate for its direct use in the manufacture offertilizer. This would be the case, for example, if fly ash had anunacceptably high concentration of heavy metals.

[0115] The increased sludge density achieved according to this inventioninfluences the size of the equipment used in the treatment process.Specifically, the size of the equipment needed in this invention isreduced when compared to the size of conventional equipment because ofthe increased density, or equivalently reduced volume, of the sludge.

[0116] Typical reactors and clarifiers 116 are modifications of standardindustrial equipment used in waste water treatment, chemical processingand mineral processing. As to the proportions of the ammonia retainingagent, precipitating agent, densifier, and pH control agent, exemplarycompositions referred to dry organic waste include about 5%-10% byweight of ammonia retaining agent, about 1% by weight of precipitatingagents, between about 0% and about 10% by weight of densifier, and about0.5% by weight of a suitable pH controlling agent, although the actualpercentages depend on the type of waste and its composition.Modifications to these proportions can be made according to knowledgecommon to those with ordinary skill in the art.

[0117] Sludge 115 from gas reactors 107 may contain zeolites if thesealuminosilicates are incorporated previously in the process; forexample, they can be added to the feed supplied to the animals in farms101 for the purpose of more effectively reducing acrid gas emissionsfrom the animals' gastrointestinal tracks. Furthermore, the addition ofzeolites to the feed supplied to the animals in farms 101 has beneficialeffects such as an improved waste slurry processing and densification,and considerable improvement of the confined animals' living conditions.

[0118] The overflow liquid 117 from the system of reactors andclarifiers 116 is fed to an aerobic lagoon system 118, which produces aliquid, or “aerobic effluent”, that meets current EPA dischargestandards and that can be used in irrigation and wetland projects 119.To this end, overflow liquid 117 in the aerobic lagoon system 118undergoes processes that include digestion and evaporation. Otherbeneficial features that distinguish the aerobic lagoon system 118 andthe liquid therein produced from their counterparts in currentstate-of-the-art treatment methods include the minimization of sludgegeneration and a significant reduction in odor production.

[0119] The solid product 120 from the reactors and clarifiers 116contains precipitated hydrous phosphates, including magnesium ammoniumphosphate. This solid product 120 is fed to a mixing reactor 121, suchas a Trommel drum, and is therein mixed, if so desired, with othercompounds that incorporate additional plant nutrients to the mixture.These added compounds can include commercial fertilizers of substandardgrades. In one of the exemplary embodiments of the mixing reactor 121, afiltrate 122 and a solid 123 are separated.

[0120] In another embodiment of the present invention, phosphates,including magnesium ammonium phosphate, can be recovered by a processknown as a RIM-NUT process, or a variant thereof Because theimplementation of this process requires higher operating costs, it isnot considered a preferred embodiment of this invention, particularlywhen applied to organic waste that does not contain toxic metals andother pollutants. A RIM-NUT process, however, could be part of apreferred embodiment of this invention if it were applied to thetreatment of, for example, municipal waste with constituents that wouldbe agrotoxins if they were incorporated into the fertilizer.

[0121] Specifically, the compounds added in mixing reactor 121 permitthe standardization of the fertilizer composition to include nutrientsin the following three classes: primary, as nitrogen (N), phosphorous(P), and potassium (K); secondary, including calcium, magnesium, andsulfur; and micronutrients, including iron, manganese, copper, zinc,boron, and molybdenum. Standardization is accomplished by analyzing theproduct 120 according to analytical methods that are commonly acceptedin the industry, determining the lowest cost compositions forsupplements to produce specific formulations of fertilizers, and thenincorporating the primary and secondary plant nutrients andmicronutrients in proportions suitable to satisfy specific marketdemands. Forms of commercially available plant nutrients that can beincorporated into the fertilizer include anhydrous ammonia, phosphoricacid, diammonium hydrogen phosphate, triple super phosphate, potassiumnitrate and potassium sulfate. Other materials can also be added at thisstage of the process if the fertilizer market demand so requires. Thesematerials include zeolites and/or perlites for purposes such as soilamendment, micronutrients, and binding and/or dedusting agents. Thisprocess allows the production of fertilizers tailored to specific marketneeds, including most standard grade compositions such as those sold as10-10-110 and 20-10-5, where each one of these sets of numbers is aconventional expression of the fertilizer composition on a weight basis.For example, a 10-10-10 fertilizer is a fertilizer with 10% nitrogen asN, 10% phosphorous as P₂O₅, and 10% potassium as K₂O. Furthermore, theprocess of the present invention is versatile enough to produce a greatvariety of fertilizers, including slow release fertilizers, that canmeet the demands and standards of a great variety of markets.

[0122] Filtrate 122 from mixing reactor 121 is fed back toreactor/clarifiers 116, whereas solid 123 is delivered to a pelletizingdrum 124. Pellets 125 are subsequently dried in dryer 126 and their sizeis standardized by means of screens 127 that separate standardfertilizer 128 from the oversized and undersized pellets 129 and 130,respectively. In one preferred size control system, oversized pellets129 are sent to a crusher 131, which delivers the crushed pellets backto screens 127 whereas the undersized pellets 130 are recycled back topelletizing drum 124. The pelletizing drum, product drier, productscreens, and crusher are standard devices widely used in the formulationof mixed fertilizers. For example, in an embodiment of this inventionproduct screens 127 are embodied by a vibrating screen system andcrusher 131 is embodied by a Stamler crusher.

[0123] When the pathogenic contents have not been entirely removed bystrong bases in clarifier 103, however, the pelletizing and separatingoperations perform necessary functions such as the elimination ofresidual pathogenic organisms, which is accomplished during the dryingof the processed manure at product temperatures as close to 100° C. aspossible. Temperatures significantly above 100° C. are not recommendedbecause struvite begins decomposing at about 100° C. and itsdecomposition would cause a significant loss of ammonia. Nevertheless,the pathogenic contents in pellets 125 may be very low or evennonexistent when strong bases, such as calcium hydroxide, are used inclarifier 103.

[0124] The final product 128 is an organic based, granular, slow releaseNPK (nitrogenphosphorous-potassium) fertilizer of standard compositionand size with micronutrients that is readily available to plants. Theprocess shown in FIG. 1 can absorb the organic waste produced by sourcesthat range from small to large scale operations. For example, theprocess shown in FIG. 1 can be implemented in farms that hold over100,000 pigs, even as many as one million pigs or more. In particular,the process can be implemented in facilities under current federalregulations for large scale confinement operations.

[0125] Because the embodiments of this invention do not require that theprocessing plant be located at the site of the organic waste source, theamount of waste produced by a single source is not a limiting factor ofthe invention. If single organic waste sources are individually smallscale operations, the elements 102-106, 108-110 in the diagram shown inFIG. 1 can be part of each single small scale organic waste source and aprocessing plant can absorb primary sludge 104 generated by a pluralityof small scale organic waste sources. This feature makes the presentinvention versatile in the sense that it can be implemented in areas ofvery diverse characteristics. Accordingly, embodiments of this inventioncan be implemented to accommodate factors such as the size and thenumber of animals in local confinement operations, particularly whenthese factors are constrained by tradition, regulations, or economicimperatives.

[0126] Because of their standard technical and operational requirements,embodiments of elements 102-106 and 108-110 can easily be retrofitted inexisting small farms, or embodiments of the entire process illustratedin FIG. 1 can be built in existing farms. Similarly, elements 102-106and 108-110, or the entire process represented by the exemplary diagramin FIG. 1, can be built at an organic waste site that is destined forclosure or cleanup. The embodiments of the present invention do notrequire that the organic waste source be a live animal confinementfacility. Furthermore, the process represented by the diagram shown inFIG. 1 can equally treat organic waste or material contaminated byorganic waste from remote sources, such as farms and animal confinementfacilities that are currently operated under conditions that are notsubject to the objectives of the present invention.

[0127] When an embodiment of the processing plant according to thisinvention is not located at the same site as the organic waste source,sludge transportation can be achieved in different ways. If the amountof sludge is large enough, and the processing plant is not so far fromthe organic waste source that pumping is prohibitively costly, thensludge transportation by pumping is preferred. Sludge is then preferablypumped at about 5% solids from a sludge storage pond at the organicwaste source to the process plant in a preferably pressurized system. Itis understood that the fraction of solid matter in the pumped sludge canwidely depend on the type of pumps and other characteristics of thetransportation system elements, as is known to those with ordinary skillin the art.

[0128] Sludge storage pond pumps are preferably grinder-type pumps,although pumps with rotating components could also be used provided thatthe sludge is free from objects that would clog pumps with rotatingparts. In an exemplary embodiment of this invention applied to a largescale operation, the combination of sludge storage pond pumps andbooster pumps preferably provides a sludge flow to the processing plantof about 54.6 l/s (about 865 gal/min) in piping that preferably isplastic piping, such as high density polyethylene piping.

[0129] The diagram shown in FIG. 1 also teaches an exemplary way ofimplementing a large scale integrated waste treatment system accordingto the present invention. This system treats waste in its solid, liquid,and gaseous forms, prevents the release of unacceptable forms of thewaste produced by organic waste sources and other sources into theenvironment, and recovers from the waste its agronutrients and energyrich components. The recovered agronutrients and energy rich componentsare made available for subsequent in-situ use or for their commercialdistribution in forms that meet environmental regulations and thatsatisfy agricultural needs and demands. FIG. 1 also teaches an exemplaryway of building an integrated waste treatment and fertilizer productionsystem according to this invention, whether this system is built duringfarm construction, or to retrofit existing farms, or as a stand aloneoperation destined to absorb waste generated in a plurality of organicwaste sources. With this versatility, the present invention is suitablefor a variety of business strategies and goals, ranging from those thatfocus on farm construction and operation savings to those that aim atindependent business profitability. Because of this adaptability to manybusiness strategies, the integrated waste treatment and fertilizerproduction process of this invention should be expected to replacecurrent waste treatment or fertilizer production processes that rely onsingle unit operations.

[0130] The exemplary embodiment shown in FIG. 1 places clarifier 103 atthe organic waste source site and reactor/clarifiers 116 at theprocessing plant site. This is only an illustration of one of thefeatures of an embodiment of this invention, but it is not a limitationto other embodiments of this invention. For example, embodiments to bediscussed below show that a reactor clarifier that can be embodied bythe appropriate facilities at the organic waste site or at theprocessing plant site. In any one of these embodiments to be discussedbelow, the reaction with the flocculent, lime, phosphate precipitatingagent, ammonia retaining agent, and optionally a densifier mostly takesplace at a single site, either the organic waste source or theprocessing plant.

[0131] The block diagram shown in FIG. 2 represents another exemplaryembodiment of the present invention. The embodiment represented in FIG.2 exemplifies a waste management and fertilizer production process for ahog farm complex, although it could equally be applied to another typeof organic waste source, such as a farm with a different type ofconfined animals. As shown in FIG. 2, ammonia adsorbing zeolite 201, oran ammonia adsorbing mixture of zeolites, is added to feed 202 suppliedto the hogs in barns 203. The addition of zeolite 201 to feed 202improves air quality in barns 203 and also decreases the release ofacrid gases from barns 203. In addition, it improves the feed conversionin animals and the overall herd health by providing a betterenvironment, reducing scours and improving the handling characteristicsof the organic waste. Furthermore, the incorporation of zeolite at theinitial stage of the process considerably reduces the reaction time ofthe overall separation. Zeolite, or a mixture of zeolites, 201 can beadded to feed 202 at a ratio of about 5% by weight in the feed. Thisamount of zeolite, however, can be varied depending on the factors thatdetermine the amount of ammonia produced by the animals; generally, itcan be added in an amount within the range of about 5% to about 10% byweight of dry organic waste.

[0132] Waste slurry 204 generated at barns 203 is subsequently treatedin reactor clarifier 205, where an ammonia retaining agent canoptionally be added. In this embodiment of the invention, ammonium andphosphates are removed from waste slurry 204 by mixing said slurry witha substance or mixture of substances 206 that causes the precipitationof phosphates, including struvite, from waste slurry 204 at an adequatepH, as discussed in the context of the exemplary embodiment shown inFIG. 1. Accordingly, a base, preferably lime, should be added to controlthe pH of the medium. This precipitating agent 206 can be, for example,magnesium chloride or magnesium sulfate, or mixtures thereof Dependingon the location, available brine of suitable composition can be used asprecipitating agent 206. Optionally, densifier 208 can also be added tothe waste slurry 204. The addition of densifier 208 improves theclarification of waste slurry 204, the quality of the NPK fertilizereventually produced, and the flocculation of colloids in the reactorclarifier 205. In essence, the addition of densifier 208 improves theprocess and product characteristics. Mineral additives or materials thatare used as densifier 208 include zeolites, perlites, crushed limestone,fly ash, clays, bentonite and mixtures thereof.

[0133] Flocculant 207 can also be added to waste slurry 204. Numerousflocculants have proven effective on waste slurries, and a variety ofsuch flocculants and their effects are given in the description of theexemplary embodiment represented in FIG. 1.

[0134] The embodiments of the present invention, however, and inparticular the exemplary embodiment represented in FIGS. 2-3, preferablycrystallize inorganic salts such as struvite; densify with porous orabsorbent minerals; and flocculate the nonsettleable matter in the wasteslurry either simultaneously or in individual steps that are proximateto each other. The high liquid-solid separation in the treatment oforganic waste achieved by the embodiments of this invention is anunexpected result that cannot be specifically attributed to any singlephysical or chemical process pathway.

[0135] The inventor suspects that the high liquid-solid separationachieved in the context of this invention is in part due to theformation of a large number of nucleation centers and to theinter-relation amongst the plurality of chemical, physicochemical andphysical processes that take place when the separation operationsperformed in the context of this invention occur in the reactorclarifier. Consequently, the present invention achieves a much betterliquid-solid separation than that performed by conventional methods.

[0136] Furthermore, the separation in the present invention isaccomplished at very high settling rates. This feature of the presentinvention leads to considerable time savings when compared withconventional separation processes.

[0137] As with the high liquid-solid separation, the very high settlingrates at which the liquid-solid separation is accomplished is anunexpected result that cannot be specifically attributed to any singlephysical or chemical process pathway. The inventor suspects that thevery high settling rates may be related to the characteristics of theseparated solid material that is consequently very effectivelysegregated from the fluid medium. These characteristics that facilitateeffective segregation and high settling rates are likely to be relatedin turn to the formation of a large number of nucleation centers and tothe interrelation amongst the plurality of chemical, physicochemical andphysical processes that take place when the separation operationsperformed in the context of this invention occur in the reactorclarifier.

[0138] Because of the inter-relation among all the species thatcontribute to the high solid-liquid separation in the embodiments ofthis invention, the terms “react”, “reaction” and their derivatives aregenerically used in the description of this invention and in theaccompanying claims, as encompassing any mixing of substances.

[0139] Sludge pumped from conventional lagoons can also be treatedtogether with waste slurry 204 in reactor clarifier 205, thus extendingthe useful life of existing conventional lagoons and reducing gasemissions therefrom. By implementing this operation, the presentinvention alleviates or even eliminates waste management problemsexperienced at conventional organic waste sources and increases theproduction of the NPK fertilizer product.

[0140] In a slightly different embodiment of the process illustrated inFIG. 2, waste slurry 204 can be separately treated in digesters andsubsequently in clarifiers. In this alternative embodiment, biogas isalso collected by floating or fixed covers and specially designedinternal baffling is provided to prevent gas bubbles from interferingwith clarification.

[0141] The phosphates precipitated by precipitating agent 206, includingstruvite, plus densifier 208, and the flocks precipitated by flocculant207 are recovered from reactor clarifier 205 as sludge 209, which is inturn dewatered by a conventional screw press 210 or equivalentfiltration equipment. The filtration process 210 produces a filter cake211 and a filtrate 212.

[0142] Filtrate 212 is fed in combination with liquid waste 213 fromreactor clarifier 205 and any liquid waste 214 from barns 203 into asystem of lagoons, initially to a primary anaerobic lagoon 215 andsubsequently to a secondary lagoon 216. Because of the extensive removalof dissolved and suspended organic and inorganic matter in reactorclarifier 205, lagoons 215-216 receive a reduced load with respect tothat received by lagoons in conventional methods, and this loadreduction causes in turn a reduction by about 50% of the required lagoonsize. This size reduction can make anaerobic lagoons economicallyfeasible in areas that are sensitive to space allocation strategies.Furthermore, the smaller size of lagoons such as lagoons 215-216 andtheir lesser loading significantly reduces the potential for waterpollution.

[0143] Because of the extensive solid-liquid separation achieved inreactor-clarifier 205 and the addition of zeolite 201 to feed 202, acridgases are incorporated into sludge 209 and subsequently into filter cake211. Therefore, odor in particular and release of gaseous products ingeneral, in the lagoon system 215-216 are dramatically reduced withrespect to the emissions of the same type of gases from conventionallagoons. The removal of solids as sludge 209 in reactor clarifier 205also significantly extends the useful life of the lagoon system 215-216and the quality of the resulting effluent water. For example, expectedtypical useful life of lagoons 215-216 is approximately 20-40 years,significantly longer than the typical useful life of approximately 10-20years for conventional lagoons. The effluent is discharged from thesecondary lagoon 216 as recycled liquid 217 that is used again in barns203, or as irrigation water 218.

[0144] Filter cake 211 that is produced in the filtration 210 is driedin a conventional design dryer 219. This dryer can be, for example, arotary, fluid bed, or flash dryer, and it produces organic base 220 thatis a pathogen free material subsequently fed to a conventional dry basisNPK granulation plant 221.

[0145] Biogas 222 is produced on a continuous basis in reactor clarifier205 by ongoing anaerobic digestion. Means for capturing this biogas 222include a floating or rigid tank cover designed to cover the clarifierand exhaust gas into a manifold that is adjacent to the overflowlaunder. Biogas 222 is delivered to dryer 219 for use as a primary fuel.The fuel supply to dryer 219 can be supplemented, if needed, byadditional fuel 223.

[0146] Exhaust 224 from dryer 219 is preferably treated in an airpollution control system 225 and then released as clean exhaust 226. Airpollution control system 225 can be in particular a conventionalbaghouse.

[0147] The dry basis NPK granulation plant produces an organic based,high analysis, NPK fertilizer product 227 whose composition can betailored for specific markets. The amount of nitrogen available ingranular NPK fertilizer 227 can be controlled by incorporating into theorganic base nitrogen compounds 228 such as ammonium sulfate, urea, ormixtures thereof The amount of phosphorous can in turn be controlled byincorporating phosphates 229 such as calcium phosphate. Similarly, theamount of potassium can be controlled by incorporating compounds 230such as potassium sulfate and potassium nitrate. The desired amount ofsecondary nutrients and micronutrients can also be incorporated into theorganic base 220 by standard methods such as adding compounds thatinclude those that provide the micronutrients listed in the descriptionof the exemplary embodiment represented in FIG. 1.

[0148] Although the organic base already contains densifiers 208, soilamendment properties of the granular NPK fertilizer can be furtheradjusted to specific needs by adding to organic base 220 materials thatinclude zeolite, perlite, diatomaceous earth, and mixtures thereof Themethod of the present invention is flexible enough to produce a granularNPK fertilizer 227 that combines one or more of the following features:high availability of nutrients, slow release characteristics, soilamendment properties, low salinity, and a suitable mix of micronutrientsin an organic base. This flexibility is made possible by the use of adry basis NPK plant, which permits the selection of the low costproducts that are used to produce the granular NPK fertilizer with themarket analysis required by specific markets. Granular NPK fertilizer227 is characterized as a high analysis fertilizer with natural slowrelease and soil amendment characteristics. These characteristics meetor exceed standards for commercial fertilizers. Furthermore, granularNPK fertilizer 227 requires no changes in existing fertilizer deliverysystems.

[0149] Like the process represented in FIG. 1, the process schematicallyrepresented in FIG. 2 can easily be adapted to utilize dredged sludgefrom existing farms for feedstock. This capability is particularlyuseful in some areas (for example in North Carolina and in Iowa) forrestoring useful life to lagoons that contain sludge accumulation aftermany years of operation according to conventional methods that do notrely on the features of the present invention.

[0150] The diagram in FIG. 3 shows another exemplary embodiment of thepresent invention. In particular, the embodiment represented in FIG. 3exemplifies another waste management, fertilizer and feed supplementproduction process for a hog farm complex; although it could equally beapplied to another type of organic waste source, such as a farm with adifferent type of confined animals. As shown in FIG. 3, ammoniaadsorbing zeolite 301, or an ammonia adsorbing mixture of zeolites, isadded to feed 302 supplied to the hogs in barns 303. Whether collecteddirectly by, for example, flushing or collected from waste pits 304,waste slurry 305 is optionally digested in anaerobic digestor 306 toproduce biogas 307 and digested slurry 308. Anaerobic digestor 306 canbe embodied by a conventional digestor used for collecting biogas suchas a digestor that comprises a tank and a receptacle for collectingreleased gas, a series of composting beds, or even a thermophillicdigestor. Biogas 307 is used as described in the discussion of theexemplary embodiments shown in FIGS. 1 and 2.

[0151] As shown in FIG. 1, biogas 111 is recovered in this exemplaryembodiment in gas reactors 107 after the separation in clarifier 103 byflocculant and prior to the reactions with phosphate precipitating agentand a base in reactor/clarifiers 116. In the exemplary embodiment shownin FIG. 2, biogas is recovered from reactor clarifier 205, whereasbiogas is recovered in the exemplary embodiment shown in FIG. 3 fromanaerobic digestor 306 prior to the reactions at reactor clarifier 312.These features of these exemplary embodiments of the optional biogasrecovery system in this invention illustrate another versatile featureof this invention, which does not require a unique order in theperformance of some of the steps in the organic waste treatment andfertilizer and feed supplement production methods.

[0152] Typically, a batch of waste slurry 305 is digested for aboutfourteen days in anaerobic digestor 306. Digested slurry 308 is thenfed, together with phosphate precipitating agent 309, lime and/ordensifier 310 and flocculant 311 to reactor/clarifier 312. Optionally,an ammonia retaining agent such as a zeolite can also be added toreactor/clarifier 312. Phosphate precipitating agent 309 can be embodiedby a magnesium salt such as magnesium chloride, magnesium sulfate or amixture thereof When a densifier is included with material 310, apreferred densifier is fly ash, and it may also or alternatively includeany of the materials that can be used as densifiers and that have beenintroduced in the discussion of the preceding Figures. Materials 309-311can be supplemented by other densifiers 208 and precipitating agent 206as discussed in the context of the exemplary embodiment shown in FIG. 2.Also, reactor/clarifier 312 can be a single unit or separate units. Whencompared to the size of clarifiers used in conventional operations, thesize of the clarifier required by this invention is much smaller becauseof the fast settling rates accomplished through the induction of a largenumber of nucleation centers upon addition of materials 309-311.

[0153] In the embodiments of this invention, the ammonia retainingagent, and in particular zeolite, is a substance that can be added, andis preferably added, in at least one of the several steps of the organicwaste treatment method. The added ammonia retaining agent is destined tobecome part of the final feed supplement and/or fertilizer producedaccording to this invention.

[0154] When the organic waste is mostly fresh manure and it is treatedaccording to the exemplary embodiment shown in FIG. 3 or an equivalentthereof, digested slurry 308 may contain an excess of ammonia that ispreferably bound by adding an acid, more preferably phosphoric acid,after the addition of magnesium salts 309 and lime and/or fly ash 310.The amount of acid to be added, and in particular the amount ofphosphoric acid to be added, is the necessary amount to approximatelystoichiometrically bind the excess ammonia. This amount can easily bedetermined by analytic techniques for quantitatively analyzing ammoniathat are known to those with ordinary skill in the art. Preferably, thephosphoric acid is added after the addition of the magnesium salt andprior to the addition of a base such as calcium hydroxide. Nitrogen in aslurry as ammonia and ammonium species combined can be determined with aTechnicon Autoanalyzer II (sold by Bran and Luebbe GmbH). The totalamount of nitrogen can be determined by the Kjeldahl method, which canbe performed with, for example, a Kjellfoss 16200 instrument. Slurry drymatter can be determined gravimetrically after oven drying at 80° C. for24 hours. Bulk pH of the slurry can be determined by means of aplurality of devices, and in particular with a standard electrode. Totalphosphorous and other species can be determined according to methodsdescribed in Standard Methods for the Examination of Water andWastewater, American Public Health Association, 17th ed., APHA,Washington D.C., 1989.

[0155] Whether the capture and extraction of plant nutrients from theorganic waste is performed by means of clarifier 103 andreactor/clarifiers 116 as shown in FIG. 1 or by means of reactorclarifier 205 or 312 as shown in FIGS. 2-3, the use of ammonia retainingagent such as zeolites, flocculent, phosphate precipitating agent andoptionally densifier leads to the effective capture of ammonia andphosphorous compounds that otherwise would be released to the atmosphereor would be part of discharged effluent. In particular, the organicwaste treatment methods of this invention lead to the effective captureof phosphorous despite its presence in organic waste in a plurality offorms. For example, phosphorous in untreated swine lagoon effluent canbe on average about 70% dissolved phosphorous and about 30% phosphorousin sediments, and it is typically found as both organic and inorganicphosphorous. The methods of this invention permit the effective removalof phosphorous from the effluent that can later be used for irrigation,wetland projects or recycled for its use at the organic waste sourcesite.

[0156] In applications where high conversion of organic phosphorous toinorganic phosphorous is desired, an optional digestor can be used forsuch conversion prior to the waste treatment in reactor/clarifier 116,reactor clarifier 205 or reactor clarifier 312. This conversion can beachieved by a digestor such as a conventional digestor used in municipalwaste treatment plants.

[0157] Sludge 313 produced in reactor/clarifier 312 is pressed in apress unit 314 which produces a filter cake 315 and a filtrate 316.Press unit 314 may be, for example, a belt press or another device thatconventionally performs an analogous function. This filtrate 316 andoverflow liquid 317 from reactor/clarifier 312 are optionally dischargedinto tank 318 where they are kept for about two days under aerobicconditions. Optionally, fluids 316 and 317 are subsequently dischargedto an intervening flow-regulating holding pond 319, from which theliquid is used for irrigation or constructed wetland projects and/orrecycled into barns 303 in, for example, waste pits 304 with optionallyadded zeolites 321. Materials 309-311 added to digested slurry 308 soeffectively separate the settleable and nonsettleable materials indigested slurry 308 that overflow liquid 317 is a clear liquid that doesnot require any anaerobic treatment.

[0158] It is understood that the addition of materials 309-311 or anyother material in the context of this invention may require the stirringof the medium into which any material is added. This operation, however,is considered within the ordinary skill in the art.

[0159] Typically, a processing plant that is part of an exemplaryembodiment of this invention and receives sludge flow at a rate of about54.6 l/s (about 865 gal/min), produces processed solution that can bereturned to the hog barns, or used for irrigation or wetland projects,at a rate of about 42 l/s (about 665 gal/min).

[0160] Although organic waste composition varies depending on theanimals, type of feed and conditions at the organic waste source, onetype of organic waste treated according to the methods of this inventionhas a composition by weight that includes about 5.2% of suspendedsolids, about 3% of total dissolved solids, or about 8.2% of totalsolids. As indicated above, zeolite can be added at several stages inthe waste treatment process, starting at the stage of supplying feed tothe barn animals. Nevertheless, an amount of zeolite of about 7 g/l inthe waste is fairly typical.

[0161] An exemplary embodiment of this invention is applied to a largescale operation with a production of 80,000 tons of dry granularfertilizer per year. In this exemplary embodiment, materials 309-310 arepreferably prepared as follows.

[0162] Calcium oxide is stored in a lime silo that can be a 50-tonstorage silo. Lime from this silo is mixed with water in anapproximately 757 l (approximately 200 gal) mixing tank by means of aconventional agitator. The lime slurry that becomes available in themixing tank is pumped when needed by a pump in a form that is anembodiment of material 310. A similar mixing process can be followedwhen fly ash is used instead of or in conjunction with lime. The pump ispreferably pneumatic.

[0163] Magnesium salts, usually magnesium chloride, are in thisexemplary embodiment available as brine, which is stored in anapproximately 37,850 l (approximately 10,000 gal) storage tank, fromwhich an embodiment of material 309 is available via a pump which ispreferably a pneumatic pump. The magnesium salts can be delivered insolid or dissolved form as the preparation of a magnesium chloridesolution from solid magnesium salts and water is an operation well knownto anyone with ordinary skill in the art. Magnesium sulfate,particularly MgSO₄.7H₂O, can also be used as a phosphate precipitatingagent in the waste treatment methods of this invention. Furthermore,soluble forms of MgO can be used both to supply required magnesium ionsfor precipitating phosphates and to increase the pH of the medium, thusreducing the amount of lime required.

[0164] An embodiment of material 311 is available from a flocculantmix-storage tank of approximately 757 l (approximately 200 gal). A waterstorage tank of about 37,850 l (about 10,000 gal) is recommended forproviding the necessary water supply for this exemplary embodiment ofthe processing plant.

[0165] In a preferred exemplary embodiment, organic waste slurry istreated with materials 309-311 according to the following process.

[0166] As shown in FIG. 4, organic waste 405 is mixed with a phosphateprecipitating agent in an approximately 227,100 l (approximately 60,000gal) tank 410 from which the mixture is transferred to a second tank 412of approximately the same capacity where it is further mixed with abase. In this exemplary embodiment, the phosphate precipitating agent isembodied by an aqueous solution of a magnesium salt 415 and the base isembodied by a slurry of calcium hydroxide obtained by mixing water andlime 425 in tank 427. The mixture is further transferred to and stirredin a third tank 414 of approximately the same capacity and it issubsequently transferred to a thickener 416 where flocculent 311 isadded. In this particular embodiment, flocculant is added to thethickener from tank 418 where thickener is prepared at a preferredconcentration. This set of three mixing tanks 410, 412, and 414, andthickener 416 is an exemplary embodiment of the reactor clarifier ofthis invention. A partial matter flow diagram for an organic wastetreatment and fertilizer production plant operating according to thisexemplary embodiment is sketched in FIG. 4. Sludge from thickener 416 ispressed in press 420 to obtain a solid that is directed to a dryerpelletizer. The overflow from thickener 416 and liquor from press 420are directed in this exemplary embodiment to purge pond 422.

[0167] As shown in FIG. 5, the reactor clarifier can optionally furtherinclude dilution tank 524 between tank 514 and thickener 516. Whendilution tank 524 is included, flocculant is preferably added to thefluid that is received in this tank, where the mixing with theflocculant takes place for its subsequent transfer to thickener 516. Inthis particular embodiment, organic waste 505 is mixed with zeolite inan approximately 227,100 l (approximately 60,000 gal) tank 509 fromwhich the mixture is transferred to tank 510 of approximately the samecapacity where it is further mixed with a phosphate precipitating agentthat is embodied in this example by hydrated magnesium sulfate 515. Themixture is transferred from tank 510 to tank 512 of approximately thesame capacity where it is further mixed with a base that is embodied inthis example by a slurry of calcium hydroxide obtained by mixing waterand lime 525 in tank 527. The mixture is farther transferred to andstirred in tank 514 of approximately the same capacity as either oftanks 510 or 512, and it is subsequently transferred to dilution tank524, where it is mixed with flocculent. In this particular embodiment,flocculant is added to dilution tank 524 from tank 518 where flocculentis prepared at a preferred concentration. This set of four mixing tanks509, 510, 512, and 514, and thickener 516 is an exemplary embodiment ofthe reactor clarifier of this invention. A partial matter flow diagramfor an organic waste treatment and fertilizer production plant operatingaccording to this exemplary embodiment is sketched in FIG. 5. Sludgefrom thickener 516 is pressed in press 520 to obtain a solid that isdirected to a dryer pelletizer. The overflow from thickener 516 andliquor from press 520 are directed in this exemplary embodiment tooverflow tank 522, from which fluid is fed to dilution tank 524.Overflow from the thickener is, in this exemplary embodiment, optionallydirected in part to the dilution tank and partially destined topost-treatment. A partial matter flow diagram for an organic wastetreatment and fertilizer production plant operating according to thisexemplary embodiment is sketched in FIG. 5.

[0168] The partial matter flow diagram sketched in FIG. 6 further showsan exemplary embodiment of some of the ammonia recovery devices thatcapture ammonia in the form of an ammonium salt. As shown in FIG. 6,organic waste 605 is mixed with a phosphate precipitating agent in anapproximately 227,100 l (approximately 60,000 gal) tank 610 from whichthe mixture is transferred to a second tank 612 of approximately thesame capacity where it is further mixed with a base. In this exemplaryembodiment, the phosphate precipitating agent is embodied by an aqueoussolution of a magnesium salt 615 and the base is embodied by a slurry ofcalcium hydroxide obtained by mixing water and lime 625 in tank 627. Themixture is further transferred to and stirred in a third tank 614 ofapproximately the same capacity and it is subsequently transferred tothickener 616 where flocculant is added. In this particular embodiment,flocculant is added to the thickener from tank 618 where thickener isprepared at a preferred concentration. This set of three mixing tanks610, 612, and 614, and thickener 616 is an exemplary embodiment of thereactor clarifier of this invention. A partial matter flow diagram foran organic waste treatment and fertilizer production plant operatingaccording to this exemplary embodiment is sketched in FIG. 6. Sludgefrom thickener 616 is pressed in press 620 to obtain a solid that isdirected to a dryer pelletizer.

[0169] To capture any ammonia that has not been incorporated into a saltor retained by zeolite or any other ammonia retaining agent, theoverflow from thickener 616 in the exemplary embodiment shown in FIG. 6is directed to tank 642, where the pH is lowered to a value preferablyin the range of about 6-7. The released ammonia is preferably convertedto ammonium sulfate in scrubber 640. When ammonia is to be recovered asammonium sulfate, scrubber 640 contains an aqueous solution of sulfuricacid at a concentration preferably in the range of about 30% to 50% byweight, more preferably at a concentration of about 40% by weight. Torecover the ammonium sulfate, the material formed in scrubber 640 isfiltered in press 641 to separate a liquid filtrate that is preferablydirected to tank 642 to lower the pH of the thickener overflow to apreferred value in the range of about 6-7. The ammonium sulfateseparated in press 641, together with the sludge from thickener 616 ispressed in press 620 to separate a solid that is directed to a dryerpelletizer, and a liquid that is directed to purge pond 622. Optionally,excess liquid from tank 642 is also directed to purge pond 622. Ammoniarecovery is enhanced by directing to scrubber 640 any ammonia that isreleased from tanks 612, 614 and thickener 616, as shown in theexemplary embodiment of FIG. 6. In addition to, or instead of, theliquid filtrate from press 641, an aqueous solution of sulfuric acid(not shown in FIG. 6) can be used to bring the pH of the medium in tank642 to a value in the range of approximately 6-7. Furthermore, theoverflow from thickener 616 can be brought to a pH in the approximaterange of 6-7 in a single tank 642 as shown in the exemplary embodimentof FIG. 6, or by a series of acid-base reactions that take place in aplurality of tanks, so that the pH is gradually reduced in acomparatively smaller amount from a value that initially is typicallyabove about 10 to a final pH in the range of approximately 6-7.

[0170] In the exemplary embodiment schematically shown in FIG. 1, thereactor clarifier is represented by clarifier 103 and reactor/clarifiers116. The reactor clarifier of this invention is represented by reactorclarifier 205 in the exemplary embodiment shown in FIG. 2, and byreactor clarifier 312 in the exemplary embodiment shown in FIG. 3.

[0171] Preferably, the organic waste is mixed first with a magnesiumsalt such as magnesium chloride or magnesium sulfate because if theorganic waste were mixed first with lime, a significant amount ofphosphate ions would combine with calcium ions, thus becomingunavailable to form magnesium ammonium phosphate. Referred to amount oforganic waste in volume, the amount of MgSO₄.7H₂O typically used is lessthan about 10 g/l, and preferably about 5 g/l, but this amount can varydepending on the type of waste and waste composition. The conversion ofthis amount of hydrated magnesium sulfate to an amount of some othermagnesium compound, such as magnesium oxide, magnesium chloride or anaqueous solution of magnesium ions is a standard operation in elementarychemistry. The addition of a magnesium salt to initiate struviteprecipitation is followed by agitation of the medium. About 15 minutesof residence time is recommended for a thorough mixing. Residence time,however, should be adjusted to accomplish extensive mixing throughoutthe waste, and thus residence time depends on the characteristics of themixed substances and the volume of the tank where the waste is mixedwith the phosphate precipitating agent.

[0172] A base such as lime is subsequently added to reach a medium pH asindicated in the discussion of FIG. 1. A pH value of about 10.5 can beaccomplished with the addition to hog waste of about 12.2 g Ca(OH)₂ perliter of mixture fed to the pH adjustment tank. The amount of pH controlagent to be added for reaching a preferred pH value depends on the baseused and on the organic waste characteristics, but pH monitoring is anoperation within ordinary skill in the art. Calcium oxide or flue dustcould also be used as pH control agent, but slaked lime with mostlycalcium hydroxide is preferred because the slaking kinetics for othersubstances is comparatively slow and a substantial excess of pH controlagent may be required to achieve a desired pH. Calcium hydroxide ispreferably added as a slurry. Phosphate that is available forprecipitation and is not recovered as struvite is available to formcalcium phosphate.

[0173] Depending on the desired strategy for germ elimination, the wastepathogenic content can be eliminated with the use of additional base toincrease the pH to about 12. For most hog waste, additional lime slurryin the amount of about 6 g Ca(OH)₂ per liter of mixture increases the pHto a value of approximately 12. A residence time of about one hour inthe pH adjustment reactor is recommended, but this time depends on thecharacteristics of the mixed substances and the volume of the tank. Forexample, a total residence time of one hour can be alternativelyrealized by two thirty-minute residence periods, one period in each oneof two reactors in series. Also, the residence time could be increasedto about two hours when pathogen content elimination is to be performedat a pH below 12.

[0174] The flocculant dosage depends on the type of flocculant used andon the suspended solids concentration. A flocculant's effectiveness,however, can be ascertained by mixing each one of a series of standardvolumes of the liquid waste with a flocculant emulsion of knownconcentration and subsequently inspecting the mixtures to determine theflocculant type and the concentration that led to the most extensiveseparation. NALCO7191 and NALCO7193 flocculants produced similar resultswith hog waste, NALCO7191 being more preferred. Volumes between about2.0 ml and about 4.0 ml of NALCO7191 emulsion at a concentration ofabout 1.0 g/l in a hydrocarbon solvent/water emulsion added to standard2-liter volumes of thickener feed at a pH of about 10.4 and at atemperature of about 20° C. that contained about 1.8% by weight ofsuspended solids produced a satisfactory separation, with a volume ofabout 3 ml of flocculant emulsion being a preferred dosage. Referred todry basis fertilizer, these dosages are approximately equivalent todosages of flocculent between about 500 mg/metric ton (about 1 lb/stdton) and about 1.1 kg/metric ton (about 2.2 lb/std ton), with about 800g/metric ton (about 1.6 lb/std ton) being preferred. Similar tests underanalogous conditions performed with thickener feed that contained about2.7% by weight of suspended solids revealed that about 500 g flocculantper metric ton of dry fertilizer had a separation efficiency similar tothe dosage of about 800 g/metric ton with the thickener feed that hadabout 1.8% by weight of suspended solids. The same dosage of about 500 gflocculant per metric ton of dry fertilizer lead to similar separationefficiency for suspended solid concentrations by weight in the thickenerfeed up to about 3.6%. The separation efficiency, however, significantlydecreases at higher suspended solid concentrations. With NALCO7191 asflocculent, the suspended solid concentrations in the thickener feedshould preferably not significantly exceed about 4% by weight, and feedswith higher concentrations of suspended solids should be diluted.

[0175] Referred to weight of dry fertilizer produced according to anembodiment of the methods of this invention, an organic waste treatmentand fertilizer production plant producing about 11.3 metric ton (about12.5 std ton) per hour requires about 15.5 metric ton (about 17.1 stdton) of zeolite per day, about 11.2 metric ton (about 12.3 std ton) ofMgSO₄.7H₂O per day, about 26.9 metric ton (about 29.6 std ton) ofCa(OH)₂ per day, and about 118 kg (about 260 lb) of NALCO7191 flocculentper day.

[0176] The size of the thickener is determined by thickening or byclarification depending on the concentration of suspended solids in thethickener feed. For example, a thickener diameter of about 18.3 m (about60 ft) is preferred for thickener feed concentrations of suspendedsolids below about 3% by weight, but the preferred diameter is about19.8 m (about 65 ft) when the suspended solid concentration in thethickener feed is in the range from about 3% to about 4% by weight. Whensuspended solid concentrations in the thickener fluid fall below about1% by weight, clarification controls thickener sizing.

[0177] Thickening refers to the increase in the amount of solids in thethickener flow that is to be pressed. Treatment of hog waste with 1.8%by weight of suspended solids at pH of about 10.4 and at atemperature ofabout 20° C. according to embodiments of the methods of this inventionproduced a sludge with an average solid content of about 10.3% by weightin a settling time of 25 minutes. Treatment of hog waste with 2.8% byweight of suspended solids under the same pH and temperature conditionsproduced a sludge with an average solid content of about 11.1% by weightin a settling time of about 35 minutes, and when the suspended solidcontent in the treated hog waste increased to about 3.6% by weight, asludge with an average solid content of about 10.8% by weight wasobtained in a settling time of about 52 minutes. The cationic flocculantNALCO7191 was employed in these thickening tests at dosages of about 750g/metric ton of fertilizer (about 1.5 lb/std ton) for the waste withabout 1.8% suspended solids, about 500 g/metric ton of fertilizer (about1.0 lb/std ton) for the waste with about 2.8% suspended solids, andabout 450 g/metric ton of fertilizer (about 0.9 lb std ton) for thewaste with about 3.6% suspended solids. In terms of the added volumes offlocculant emulsions, about 2.8 ml of the cationic flocculant emulsionat a concentration of about 1.0 g/l were added to about 2 l of liquidwaste that contained about 1.8% of suspended solids; about 3.0 ml andabout 3.2 ml of the same flocculant solution were added to the samevolumes of liquid waste with about 2.8% and about 3.6% of suspendedsolids, respectively.

[0178] As the preceding discussion indicates, a feature of thisinvention is that the organic waste treatment and fertilizer and feedsupplement production methods can be implemented according to batch orcontinuous processes. A process that obeys a batch design is conductedin a single agitated tank with reagents added sequentially, the solidssettled, overflow decanted, and the settled solids removed for furtherdewatering and drying. An exemplary embodiment of this operational modewould include three 18.3 m×18.3 m (60 ft×60 ft) tanks employed inrotation in 24-hour cycles. Small scale operations may benefit frombatch processes. Although a continuous process requires more control andoperating attention, it may be more cost effective for large operations.

[0179] Instead of, or in addition to, the use of phosphoric acid tocapture excess ammonia as it has been described above, scrubbers can beused to increase ammonia recovery, as exemplarily shown in FIG. 6. Tothis effect, gases released at the stage of and at stages subsequent tothe treatment with a basic compound such as slaked lime are directed toscrubbers that contain an acidic solution such as a dilute aqueoussolution of sulfuric acid, where ammonia is captured by formation ofammonium salts with the acid in the scrubber. This recovery processalone or in combination with the addition of phosphoric acid asindicated above significantly increases ammonia recovery. For example,the use of scrubbers to capture the ammonia released at stagessubsequent to the treatment with a pH control product such as slakedlime leads to ammonia recovery that can be as high as 90% relative tothe ammonia originally present in the organic waste. The technology forrecovering ammonia gas by means of scrubbers with sulfuric acid has beenextensively developed and is well known for recovering ammonia emissionsfrom coke ovens. The ammonium salts formed in the ammonia recoveryprocess are preferably incorporated in the fertilizer production processat a stage prior to the formation of an organic base. For example, thesesalts can be mixed with sludge 313.

[0180] For example, FIG. 7 partially shows an embodiment of an ammoniascrubber in which ammonia is recovered mostly as ammonium sulfate.Ammonia containing gas is blown in vessel 710 with blower 720, where theblown gas is mixed with aqueous solution of sulfuric acid that is fedinto vessel 710 at a concentration in the range indicated in thediscussion of FIG. 6. Vent gases are preferably treated in stripper 730to separate any ammonia prior to their release into the atmosphere, andthe recovered ammonia is directed to vessel 710. Ammonium sulfate isseparated in separator 740 and directed to, for example, press 641 shownin FIG. 6. The solution and any gas separated in separator 740 areredirected to vessel 710 that is typically equipped with device 750 forregulating the liquid level to a desired height within vessel 710. See,for example, Vincent Sauchelli, Chemistry and Technology of Fertilizers(1960) pp. 33-34, which is hereby incorporated by reference in itsentirety for the material disclosed therein.

[0181] Because the presence of ammonia as ammonium ion in an aqueoussolution or its conversion to ammonia gas depends on temperature and pH,known relations that express the percentage of ammonia as ammonium ionand as ammonia gas are typically utilized in ammonia recovery processes.These relations are within the ordinary skill in the art and they areusually employed in the form of graphic representations, as the oneshown by way of example in FIG. 8. The graph shown in FIG. 8 displaysthe weight percentage of ammonia as ammonium ion and as ammonia gas atdifferent pH values at the temperatures of ° C., 20° C., and 40° C. Forexample at a temperature of about 20° C., an aqueous medium with a pH ofover 10 would contain not more than about 20% of the ammonia as ammoniumions in solution and at least about 80% of the ammonia as ammonia gas.In contrast, an aqueous solution at the same temperature with a pH ofabout 7 would contain almost all the ammonia as ammonium ions insolution, but almost no ammonia as ammonia gas.

[0182] As exenplified in FIG. 3, a preferably pneumatic sludge pumpdelivers sludge 313 from the thickener to a system of three belt pressesthat constitute an exemplary embodiment of press 314. In this exemplaryembodiment, a surge pond replaces tank 318 and exemplarily embodiesholding pond 319. The surge pond in this example holds approximately18,925,000 l (approximately 5,000,000 gal) of filtrate 316 and overflow317. In this embodiment, overflow 317 comprises thickener overflowliquor that is rejected from the system to maintain the appropriateconcentration of total dissolved solids at a value that allows for themaximum flocculant separation efficiency as discussed above.

[0183] Filter cake 315 is preferably conveyed by a bucket elevator to adryer-pelletizer unit that exemplarily embodies dryer (agglomerator)322. A bucket elevator is an exemplary embodiment of a means fortransporting a solid or semisolid material. Depending on the consistencyof the material to be transported, this means for transporting can beembodied by other devices, such as a conveyor belt. The dryer-pelletizerunit typically includes a feed bin with a screw feeder to deliver filtercake to a manure dryer that preferably burns propane or a combination ofpropane and biogas 307. In this exemplary embodiment, propane only isfed to the manure dryer from two propane tanks which hold about 75,700 l(about 20,000 gal) each.

[0184] The set of devices shown in FIG. 1 comprising pelletizing drum124, product dryer 126, product screens 127, and crusher 131, or the drybasis NPK granulation plant 221 in FIG. 2, or the dryer (agglomerator)322 in FIG. 3 can be embodied for example by the dryer/pelletizer unitschematically shown in FIG. 9.

[0185] As shown in FIG. 9, solid from a press that can be exemplified bypress 314, press 420, press 520, or press 620, is conveyed to a feed binto subsequently be treated in an agglomerator dryer. Thermal energy forthe dryer can be provided by burning propane and/or biogas, such asbiogas 111, 222, or 307. The solid product from the agglomerator dryeris conveyed to a vibrating screen, whereas the particulate matter in thegaseous products from the agglomerator dryer is preferably separated bymeans of a cyclone and a bag house and then the gaseous products arereleased into the atmosphere. The solid product from the agglomeratordryer is preferably size selected by a vibrating screen system, and itis either stockpiled as granulated manure when it has a specified sizeor fed back to the feed bin, with or without crushing, when the size isnot appropriate. After size selection, the granulated manure obtained inthis embodiment that exemplifies a dryer/pelletizer unit of the organicwaste treatment and fertilizer production processes of this invention ismarketed directly as a fertilizer.

[0186] As shown in FIG. 3, filter cake 315 is treated in unit 322 whichincludes a dryer and also an agglomerator if needed. The dried productis organic base 323 which can be used in the preparation of fertilizer324 as described in the context of the exemplary embodiments shown inFIGS. 1 and 2 and/or as feed supplement 325. Depending on the pH ofdigested slurry 308, which in turn depends on the amount of basiccompounds in materials 309-311 added to reactor/clarifier 312, organicbase 323 may have to be neutralized with a pH control agent 326 prior toits use as feed supplement 325. The practice of this neutralizationoperation is known to those with ordinary skill in the art. This pHcontrol agent 326 includes, but it is not limited to, acidic wood sugarand equivalent conventional additives and mixtures thereof Wood sugaralso improves the quality of the feed supplement in the sense that itimproves its taste to animals.

[0187] It is understood that when a pH control agent, such as woodsugar, is needed for producing a feed supplement for animals it can beadded to any or several of solid 123, sludge 209 or 313, filter cake 211or 315, and organic base 220 or 323.

[0188] The product exemplified in FIGS. 1-3 by solid 123, organic base220, and filter cake 315 or organic base 323 may have a relatively highpH due to the use of a basic product in the waste treatment process. Oneof the features of this invention is the production of fertilizer whosecharacteristics are tailored according to specific regional variables.For example, fertilizer produced for regions with high soil pH willrequire pH control of the fertilizer prior to its delivery. In this casethe pH of the solid 123, the organic base 220 or 323, or filter cake 315should be lowered by adding acidic compounds that are well known formodifying fertilizer composition and preparing soil amendments. A highpH fertilizer, however, is desirable for regions with low pH, andminimal or no pH control of the solid 123, the organic base 220 or 323,or filter cake 315 may be needed.

[0189] Fertilizer is usually handled in granulated form. Therefore,embodiments of the fertilizer production methods of this inventioninclude a granulating step that can be embodied in a variety of forms.For example, the granulating of the fertilizer is represented in theembodiment shown in FIG. 1 by items 124-127 and 129-131. It isrepresented by granulation plant 221 in the embodiment shown in FIG. 2,and no explicit reference to the granulating step is made in theembodiment shown in FIG. 3 because drying and granulating a filter caketo form pellets or grains of standard size is a known operation to thosewith ordinary skill in the art.

[0190] Analogously, only the exemplary embodiment shown in FIG. 2explicitly refers to the supplementing of organic base 220 to make thedry basis NPK fertilizer at plant 221. The analysis of a fertilizer andadditives to be used to make a NPK fertilizer of standard compositionand optionally supplement it with micronutrients and soil amendments areconsidered to be part of the ordinary skill in the art and only thesteps of supplementing the organic base are explicitly referred to. Itis understood that supplements to achieve a NPK standard composition,micronutrients or soil amendment materials can be added at severalstages in the fertilizer production methods of this invention. Thesestages include in particular those at mixing reactor 121, filter cakes211 and 315, and organic base 220 and 323. Furthermore, some of thesubstances with which the organic waste itself is treated can befertilizer supplements. For example, some zeolites and densifiers arealso suitable soil amendments when they are incorporated into the soilwith the fertilizer of which the densifiers and zeolites are an integralpart of.

[0191] An important feature of this invention is that it can beimplemented in the form of embodiments that require no lagoons. Inparticular, the exemplary embodiment described by the diagram shown inFIG. 3 requires no lagoons. This is an important feature of thisinvention because, under current regulatory schemes, some states imposebuilding moratoria on hog farms that rely on technologies that uselagoons, but exempt units that rely on technologies that do no requirelagoons.

[0192] One of the features of the embodiments of this invention is theproduction of a liquid and a precipitate. The liquid can be recycled forirrigation, for wetland projects, or for its use at the organic wastesource and the precipitate comprises the materials of agronomic valueand the substances in the organic waste that would become pollutants ifthey were released in the environment.

[0193] The liquid comprises the liquid fraction from the organic wastetreatment with phosphate precipitating agent, base, flocculant,optionally ammonia retaining agent and optionally densifier. Forexample, this liquid is embodied by overflow liquid 117 treated inaerobic lagoon system 118 in FIG. 1, by filtrate 212 and recycle liquid217 in FIG. 2, and by filtrate 316 and overflow 317 in FIG. 3.

[0194] The precipitate comprises the materials obtained from the reactorclarifier that will eventually become fertilizer and/or feed supplement.This precipitate can be embodied in different forms at different stagesof the several exemplary embodiments of the organic waste treatment andfertilizer and feed supplement production methods of this invention. Forexample, the precipitate is referred to as solid product 120 and solid123 in FIG. 1; as sludge 209, filter cake 211, and organic base 220 inFIG. 2, and as sludge 313, filter cake 315 and organic base 323 in FIG.3.

[0195] In the exemplary embodiments of this invention in which thereactor clarifier comprises more than one stage, such as clarifier 103and reactor/clarifiers 116 in FIG. 1, the obtention of the precipitateis preceded by the formation of a primary sludge 104 and optionally bythe formation of degasified sludge 115. Whether a primary sludge isformed or not, the precipitate in this invention comprises thesettleable and nonsettleable materials in the organic waste. Thissettleable and nonsettleable materials are obtained in a highsolid-liquid separation at very high settling rates by mixing theorganic waste with an ammonia retaining agent, flocculant, phosphateprecipitating agent, base, and optionally densifier.

[0196] The schematic and exemplary block diagrams shown in FIGS. 1-3illustrate some of the important characteristics of this invention.These characteristics include: (1) the reduction, or elimination, ofacrid gas and greenhouse gas release, (2) the conversion of organicwaste into effluents with reduced or no polluting levels of COD and BOD,(3) the availability of effluent for irrigation or wetland projects atthe sites where the farms and the processing plant are located, (4) thereduction of lagoon size by diminishing lagoon load or even theelimination of the use of lagoons, (5) the recovery of methane-richbiogas that can be used for thermal and electrical energy generation andfor synthetic and catalytic processes, (6) the beneficial and usefulprocessing of organic and industrial residues, such as organic waste andfly ash, and mining products such as clays, (7) the demand for naturallyoccurring or low cost processing materials, such as zeolites, brine andlime, (8) the production of an organic based fertilizer whosecomposition and size are standardized, that is readily available toplants by slow release and that can be supplemented to contain themicronutrients that plants need for survival and growth, (9) thetreatment of organic waste with no requirements of selective ionexchange columns, ion exchange resin regeneration, or ion exchangeresins, and (10) the treatment of integral organic waste, namely, thisinvention does not require the separation of the waste into a pluralityof solutions with merely a few chemical species each.

[0197] The schematic diagrams shown in FIGS. 1-3 are not meant to bemutually exclusive. On the contrary, process steps represented in theseFigures can be suitably combined to generate processes that areadditional exemplary embodiments of the present invention. Theseadditional combinations however, can be performed with the aid of theobjectives and teachings herein contained and ordinary skills in theart; thus no other combinations are offered as additional explicitexamples. Furthermore, redundancy has been avoided wherever possible bydescribing in detail only once any individual step that repeatedlyappears in several exemplary embodiments. Consequently, a detaileddescription of any given process step in any exemplary embodiment isalso descriptive of the same or an equivalent process step in any otherexemplary embodiment herein considered or equivalents thereof

[0198] The present invention may be embodied in other specific formswithout departing from its spirit or essential characteristics. Thedescribed embodiments are to be considered in all respects only asillustrative and not restrictive. The scope of the invention is,therefore, indicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

hat is claimed and desired to be secured by U.S. Letters Patent is:
 1. Amethod for treating organic waste, comprising: mixing organic wastehaving unseparated settleable and nonsettleable material with at least aflocculant to produce a mixture, wherein said unseparated settleable andnonsettleable material is present in said organic waste in excess ofwhat said material would be present in a supernatant solution obtainedfrom a primary lagoon treatment of waste; obtaining a sludge from saidmixture; and mixing said sludge with at least a phosphate precipitatingagent.
 2. A method as recited in claim 1, wherein said mixing organicwaste is performed at a first treatment site and said mixing said sludgeis performed at a second treatment site, and said first treatment siteis different from said second treatment site.
 3. A method as recited inclaim 1, wherein said flocculent comprises a cationic polyacrylamide. 4.A method as recited in claim 1, wherein said mixing organic waste havingunseparated settleable and nonsettleable material comprises mixing withlime.
 5. A method as recited in claim 1, wherein mixing said sludgecomprises mixing with an ammonia retaining agent.
 6. A method as recitedin claim 1, wherein mixing said sludge comprises mixing with adensifier.
 7. A method as recited in claim 1, wherein mixing said sludgecomprises mixing with a pH control agent.
 8. A method as recited inclaim 1, wherein said mixing said sludge produces a solid product, andfurther comprising standardizing said solid product to form afertilizer.
 9. A method as recited in claim 8, wherein saidstandardizing comprises mixing said solid product with at least one ofnitrogen-based nutrient, potassium-based nutrient, phosphorous-basednutrient, and mixtures thereof.
 10. A method as recited in claim 8,wherein said standardization comprises mixing said solid product with atleast one of calcium-based nutrient, magnesium-based nutrient,sulfur-based nutrient, and combinations thereof.
 11. A method as recitedin claim 8, wherein said standardization comprises mixing said solidproduct with at least one of iron-based micronutrient, manganese-basedmicronutrient, copper-based micronutrient, zinc-based micronutrient,boron-based micronutrient, molybdenum-based micronutrient, and mixturesthereof.
 12. A method as recited in claim 8, further comprisingpelletizing said fertilizer.
 13. A method as recited in claim 1, whereinsaid phosphate precipitating agent comprises at least one magnesiumsalt.
 14. A method as recited in claim 1, wherein said organic wastehaving unseparated settleable and nonsettleable material is digested toobtain biogas prior to said mixing with at least a flocculant.
 15. Amethod as recited in claim 1, wherein said mixing said sludge with atleast a phosphate precipitating agent produces a solid product and saidsolid product is obtained in a batch process.
 16. A method as recited inclaim 1, wherein said mixing said sludge with at least a phosphateprecipitating agent produces a solid product and said solid product isobtained in a continuous process.
 17. A method as recited in claim 1,wherein said mixing said sludge produces a product, and furthercomprising mixing said product with a pH control agent to obtain a feedsupplement for animals.
 18. A method as recited in claim 17, whereinsaid pH control agent comprises wood sugar.
 19. A method as recited inclaim 1, wherein said mixing said sludge produces a product, and furthercomprising mixing said product with a pH control agent to obtain apH-regulated fertilizer for soil amendment.
 20. A method for treatingorganic waste, comprising: mixing organic waste having unseparatedsettleable and nonsettleable material with at least a phosphateprecipitating agent to produce a mixture, wherein said unseparatedsettleable and nonsettleable material is present in said organic wastein excess of what said material would be present in a supernatantsolution obtained from a primary lagoon treatment of waste; andobtaining a sludge from said mixture.
 21. A method as recited in claim20, wherein said mixing organic waste comprises mixing with a densifier.22. A method as recited in claim 20, wherein said mixing organic wastecomprises mixing with a flocculant.
 23. A method as recited in claim 21,wherein said densifier comprises at least one of zeolite, perlite,crushed limestone, fly ash, clay, bentonite, and mixtures thereof.
 24. Amethod as in claim 20, wherein said phosphate precipitating agentcomprises at least one magnesium salt.
 25. A method as in claim 20,further comprising separating from said sludge a filter cake.
 26. Amethod as recited in claim 25, further comprising drying said filtercake to obtain an organic based product.
 27. A method as recited inclaim 26, further comprising adding to said organic based product atleast one of a nitrogen-based compound, a phosphate, a potassium salt,and mixtures thereof, to obtain a fertilizer.
 28. A method as recited inclaim 26, further comprising adding to said organic based product atleast one of calcium-based nutrient, magnesium-based nutrient,sulfur-based nutrient, and combinations thereof, to obtain a fertilizer.29. A method as recited in claim 26, further comprising adding to saidorganic based product at least one of iron-based micronutrient,manganese-based micronutrient, copper-based micronutrient, zinc-basedmicronutrient, boron-based micronutrient, molybdenum-basedmicronutrient, and mixtures thereof, to obtain a fertilizer.
 30. Amethod as recited in claim 26, further comprising pelletizing saidorganic based product to obtain granular fertilizer.
 31. A method asrecited in claim 20, wherein said organic waste having unseparatedsettleable and nonsettleable material is digested to obtain biogas priorto said mixing with at least a phosphate precipitating agent.
 32. Amethod as recited in claim 20, wherein said sludge is obtained in abatch process.
 33. A method as recited in claim 20, wherein said sludgeis obtained in a continuous process.
 34. A method as recited in claim25, further comprising mixing said filter cake with a pH control agentto obtain a feed supplement for animals.
 35. A method as recited inclaim 33, wherein said pH control agent comprises wood sugar.
 36. Amethod as recited in claim 25, further comprising mixing said filtercake with a pH control agent to obtain a pH-regulated fertilizer forsoil amendment.
 37. A method for treating organic waste, comprising:mixing organic waste having unseparated settleable and nonsettleablematerial with at least a flocculant to produce a mixture, wherein saidmixing is performed with said organic waste when said organic waste hasnot been subjected to a primary lagoon treatment of organic waste;obtaining a sludge and a liquid fraction from said mixture; and mixingsaid sludge with at least a phosphate precipitating agent.
 38. A methodas recited in claim 37, wherein said mixing organic waste is performedat a first treatment site and said mixing said sludge is performed at asecond treatment site, and said first treatment site is different fromsaid second treatment site.
 39. A method as recited in claim 37, whereinsaid mixing said sludge further comprises mixing with at least one of anammonia retaining agent, a densifier, a pH control agent, and mixturesthereof.
 40. A method as recited in claim 37, wherein said mixing saidsludge with at least a phosphate precipitating agent produces a solidproduct and said solid product is obtained in a batch process.
 41. Amethod as recited in claim 37, wherein said mixing said sludge with atleast a phosphate precipitating agent produces a solid product and saidsolid product is obtained in a continuous process.
 42. A method fortreating organic waste, comprising: mixing organic waste havingunseparated settleable and nonsettleable material with at least aphosphate precipitating agent to produce a mixture, wherein said mixingis performed with said organic waste when said organic waste has notbeen subjected to a primary lagoon treatment of organic waste; andobtaining a sludge and a liquid fraction from said mixture.
 43. A methodas recited in claim 42, wherein said mixing said organic waste furthercomprises mixing with at least one of an ammonia retaining agent, aflocculent, a densifier, a pH control agent, and mixtures thereof.
 44. Amethod as recited in claim 42, wherein said sludge is obtained in abatch process.
 45. A method as recited in claim 42, wherein said sludgeis obtained in a continuous process.